Empathy Yahoo IM contact request spam
Solution 1:
The real problem here, from my perspective, is the fact that Empathy doesn't reject requests properly. I keep having the same requests pop up every time even after I reject them until I use pidgin or some other messenger to reject the request. The Empathy team needs to fix the reject request function properly.
Solution 2:
I've had this problem as well, and sadly, it's is really a problem with Yahoo's infrastructure, and not so much something wrong with empathy (in other words, you won't be able to stop empathy from thinking you have genuine friend requests).
The best I can suggest to you is to report a wishlist bug on empathy :(. You could try pidgin but to my memory, that doesn't make it too much easier to dismiss the contact spam in one go, though it does handle it better than empathy.
As grim as it sounds, I'd also suggest moving away from yahoo for IM.
Solution 3:
If you have a copy of Windows, I'd recommend running Trillian and rejecting the people through there, or running a copy of the Yahoo IM client (ugh). That's how I got rid of the requests in Empathy, but then again, I dual boot. I don't know how feasible this is for you.
I second filing a bug for mass-rejection.