This is definitely true for me too. I've wondered -- do I find my friends attractive because I love them as friends, or because I subconsciously pick hot friends?
Luckily, most of my friends are pretty chill about casual sexual interactions if they happen to happen (ranging from snugglingto a drunken makeout session to fuckin') and aren't squicked by bisexuality (thus avoiding the "my same gender friends flee me!" problem described above), so it's never really been a problem.
I think for people who aren't hardwired mono these sorts of attractions must be pretty common, no?
Of course, I could see it being a major logistical problem if you tried to partner with all your friends and they weren't open to the idea of forming a commune!