I've seen many lists running
Wear // Tear in the sideboard; however, I'm having some trouble understanding exactly why this card would be preferable to oblivion ring. First off, based on what's currently being played I think that you will almost never get a 2-for-1 with wear//tear (except for against Imperial Painter), so I think it's safe to ignore this aspect of wear//tear for the most part. Now, oblivion ring can be used against anything wear//tear can be used against, so we'd want oblivion ring whenever we'd want wear//tear as well.
I'd like to consider the downsides (that I notice) when using oblivion ring compared to wear//tear as an answer to artifacts and enchantments. These are: higher mana cost, the fact that your opponent could potentially get their card back, and lack of instant speed. While certainly issues, all of these seem like potentially small drawbacks most of the time. I think against decks wear/tear is best against, you'll probably leave in enough other permanants (balance, RIP, Clique), to where those decks would already have plenty of targets. To me, the fact they can destroy Oring is probably the largest argument to not run it. The mana cost could be relevant occasionally, although most decks you want artifact and/or enchantment hate don't seem to be particularly fast, so you should have the time to play a card which is slightly slower. Instant speed is definitely useful, with the most significant application at trying to get a Batterskull or leaving countermagic mana open, but I think more often than not you'll be okay to tap three mana for an oblivion ring in one turn.
Now the upsides (in my opinion) for oblivion ring are increased flexibility (in terms of what permanent you need to answer), incredible usefulness against a show and tell, and additional ways to answer planeswalkers. To me, it seems like all three of these reasons will, in general, be a much stronger reason to choose oblivion ring over wear//tear. I think very few decks are running must-answer artifacts and/or enchantments where you're very concerned with the downsides that I mentioned above.
Now, I haven't used wear//tear at all, and I could be completely downplaying the negatives (or missing some huge ones entiredly), but it seems that oblivion ring's flexibility and usefulness in more matchups outweighs the relative benefits wear//tear gets, based on how narrow it is. If somebody could help me understand why wear//tear would be preferable to Oblivion Ring currently, I would much appreciate it.
EDIT: Pretty sure creature heavy lists should have 4 Baleful Strix :P