I had mentioned this on another thread but I thought it deserved a thread of it's own.
I was at the pub last Friday night and no-one believed me when I said "if a really hot girl came up to me now and wanted sex with me, I would say no". All the other guys gave me dodgy looks in a, what are you talking about way. Everyone thought I was lying, males and females.
I'm not saying I never consider it or have never been in a situation where it's likely to happen, but I don't want have sex randomly with some girl I hardly know.