The number of people you've had sex with. It doesn't necessarily have to be in a bed. One's bed count can be reduced by adjusting for Fractional Sex experiences. Bed count is similar to Head Count, the number of times you've performed oral sex.
Claire: "I so wanna fuck that Kyle guy, but I'm already up to four guys. Five's too high for a bed count."
Janine: "Yeah, but if you only count the ones who really mattered, I'm sure you'd be down around 2 or 3, you know, fractional sex. You've had some shitty luck with the guys you've done."
Clarie: "You're right. I'm gonna go for it!"