I heard that on Chemistry, and well, as much as it is something said in a fit of anger, there is some truth in it. Not that you can't trust your best friend, but you can't trust your boyfriend with your best friend. Especially if you've got a good-looking best friend. I mean, doesn't anyone out there worry about boyfriends/girlfriends being attracted to one's best friend? Unless they hate each other's guts, which, IMO, with a whole lotta narrativism is gonna only go one way. You know, you've seen it. People who are always at each other's throats habour a great and deep attraction to each other. Unless they really hate each other's guts.
But back to my rather off-handed topic at hand. There's always a danger of that ain't it? Especially if you're trying desperately to juggle time between both of them, and end up seeing both of them at the same time. What if your gf/bf likes your friend better? What if he/she begins to REGRET being with you? I'm probably being paranoid here, but I HAVE had this fear before, and sometimes when I introduce the guys I like to my best friend, it becomes a sort of test. If they mention anything about her being extremely good-looking, chances are, I'll rapidly begin to lose all interest in him. Because I'm such a jealous bitch, you know. I've never been very secure about myself, and if I'm going to get saddled with someone who looks at other girls and has the audacity to mention it to me, sorry, not going there. Speaking of which, it's time for me to work on the Seven Deadly Sins of Dating. Apart from the lust and coveting. Seriously.
People say "Ugly Chicks have good looking friends." I sure as hell ain't the best looking one. Heh.