I'm not a yoai fan. I don't have a problem with it in general, it's just that some *coughmostcough* fans try to put EVERY boy anime character in a yoai pairing. If it actually relates to the anime, I don't really mind it any more than any normal couple. The thing is, there aren't many of those, almost every male/male pairing I know of is fan-created. Some examples of "fan" yoai pairings are Ryou/Bakura (Yu-Gi-Oh) and Kurama/Hiei (Yu Yu Hakusho). No offense to fans of these pairings, but Ryou and Kurama are some of my all time favorite anime characters, and I find these pairings slightly offending.
Male/male pairings actually suggested in the anime itself aren't as bad. Not very common either, especially when you like mostly shounen (boys) anime/manga series'. (Yes, I am a girl, and yes, I like shounen more than shoujo.) Anyways, to the one and only yoai (well, it's mre of shounen-ai, but its male/male) couple I like at all. Kaworu/Shinji, from Evangelion. Kaworu actually says that he loves Shinji, and seems to really show signs of it, too. It seems like an actual part of the anime itself, especially since from what I've seen on the internet, the creator supports the couple. Ok, now I'm done talking (and talking, and talking, and talking...