As far as I'm concerned, Blizzard not only doesn't frown on stuff like this, but they encourage it. Their systems are easily exploited, they will take no action to help those that get screwed, and probably worst of all, they have an official trade forum. If they don't think it's a good idea to trade with random players, why the fuck do they have a forum whose sole purpose is to encourage trading with random players? That just seems like the most backwards logic possible to me.
There's a damn good reason I refuse to use any means of trading that's not the AH, unless it's with a RL friend. And really, the only trading I do with RL friends, is with a friend that plays in the same room as me.