Patrick Chapin posted this on twitter:

Originally Posted by thepchapin:
Library of Alexandria is not being placed on Online Classic Restricted List (when other ME4 cards are). Is this a hint as to next B/R list?
People are speculating that Library not restricted in Online classic (whereas other card from paper restricted list are restricted on onlineclassic too) could be an hint for a soon to be unbanned LoA in paper magic, or at least a sort of "test" to see how the card would perform in the modern era. As far as i know, Library has been banned/restricted for as long as it came out basically, so i've never played with the card and i never witnessed its power level.
However, i can see easily a couple of things:

- LoA promote brown, mono and bi-color decks especially by being another land that you want to run in 4
- LoA would cost 200+ if it come off the R/B list
- LoA is insane in control mirror

I found this interesting old article from Smennen that talked about library:

Quote Originally Posted by Smennen
Crucible of Worlds Should be Restricted Because...
Here I'm going to present the arguments for restriction. Any criticism of these arguments will have to wait until I've laid out the arguments for restriction.

1) Crucible is the New Library of Alexandria

Black Vise is certainly a card that fits the "excessively distorting" bill without necessarily producing a dominant archetype. Some people think Crucible is the new Black Vise. I think not. To say that Crucible is the new Library of Alexandria is a nuanced way of saying that Crucible is "excessively distorting" without going so far as to call it Black Vise. In terms of function and effect, Library is admittedly fairly close to Crucible.

Let's, for the moment, ignore all matches except the control mirror. There are three cards that commonly break open control mirrors: The first two provide built-in inevitability: Yawgmoth's Will and Mind Twist. You can have parity until a very late game position when either of those cards will win you the game if they resolve. The third is Library of Alexandria. Library of Alexandria is different, because if unanswered for a few turns in the early game, it will push you so far ahead that you can't lose. This is particularly evident in control matches where there is no way to deal with it, such as the Tog mirror.

I know that Library of Alexandria would also be strong in decks like Fish, but ignoring that for the moment, unrestricting Library of Alexandria could seem like a plausible argument at first glance because it doesn't really affect the Aggro or Combo matchups. Library is pretty terrible against Belcher or Tendrils Combo. Most Control mana bases couldn't afford to run lots of Libraries, but might sideboard some in for control mirrors. Nonetheless, what Library does is sufficiently degenerate that unanswered it will win games by itself. Because Library affects the short-game and not the inevitability of the deck, is it often more egregious in control mirrors when seen than Mind Twist and Yawgmoth's Will. In other words, instead of forcing decks to duel it out for a while using skill and strategy to resolve your bomb, Library just appears and steals the game early on unless your opponent can kill it.

Crucible is like all three cards. Crucible comes down, and if unanswered and combined with Wasteland will win the game in a very similar manner to Library. However, it is also like Mind Twist and Yawgmoth's Will. It gives you inevitability, because eventually you will find Strip Mine and win.

Library of Alexandria is a great card to measure against to test the distortion criteria. Suppose Library of Alexandria were to be unrestricted. It wouldn't shatter the format, nor produce a single dominant deck. Many Control decks would run 2-3 (probably not four, because you need sufficient Blue-producing lands) and most Aggro-Control decks would do the same. Libraries would heavily distort control matches in that the player who gets to abuse Library the most will probably win - making Control matches more luck and design-based than skill-based. It would be played in most control and aggro-control decks and suck the skill from these matches. The real problem is that you have to have a way to deal with it, or lose the game. Therefore, it squeezes out Control decks that don't have room for 4-9 colorless lands.

Similarly, the argument for restricting Crucible of the Worlds is that it is distorting the format in terms of deck design and in terms of what can be successful and what can't.

The argument runs as follows. Decks that have multi-color mana bases that don't intend on winning in the first few turns basically must use Crucible or be prepared to deal with Crucible (much like one must either use LOA or be prepared to deal with it if it were unrestricted). So far, some decks have addressed the Crucible issue by upping their basic land count. A few decks can't do that. In other words, Crucible could potentially push out decks like Four Color Control unless they also abuse Crucible, turning certain decks into Crucible decks and decks that are immune to Crucible such as Mono--Blue, Control Slaver and Combo. Of course, that says nothing about their capacity to beat Aggro or Combo, but the Control mirror is a very important matchup in Type One. There are many control variants out there and many of the best players play Control such that if you can't win some of the control matches, you can't win tournaments. In my mind, this is the most serious problem with Crucible - it effectively distorts what will happen in the control mirror.

Now that we have looked at the control mirror, we need to look at what happens in other matchups.

Combo v. Control: Crucible is probably irrelevant.

Control v. Aggro: Crucible is relatively unimportant.

Aggro v. Combo: Crucible is terrible.

Aggro v. Aggro-Control: Crucible could be important.

Doesn't restricting because of the Control v. Control matchups seem to go a little far? In other words, if the only matchup which is distorted is Control v. Control, does that make it "excessively" distorting, such that it will warrant restriction under the second criterion? Possibly not. But there is another side to the Control mirror issue.
In the arcticle (full version here), Smennen talked about how Crucible break the control mirror and how Crucible is similar to Library in various aspect. History told us that Crucible didn't break anything in Vintage nor in Legacy, and honestly, if there is a card that totally break control mirrors nowadays, that's Jace. Jace is very similar to Alexandria in the sense that when it get down in a control mirror, the guy who played it win the game almost always.
Obviously, Alexandria is a land, meaning that in control mirror you can't counter it, but i believe the main point here is that Wizards seems "ok" printing cards that completely distort a matchup given that matchup is not too common and given also enough good and cheap answers for it in the format (case of Jace: creatures, permission, double-bolt, needle, etc... in case of LoA: needle, wasteland, tsabo's lol, Rishadan port, etc...)

Do you think Wizards is onto something here with this move? It's just an experiment or a more serious issue?

Personally, while i think an experiment with LoA in Legacy could be interesting (or Vintage), i think LoA pose too much emphasis on "luck" to be removed from the list. If you are lucky enough, you get a fast library down and when active it can draw you a lot of card fast. If you aren't, LoA is a terrible card. Before unrestricting/unbanning LoA i'd honestly unban a lot of other things.
Your thoughts?