So, I'm going to temper my response a little in my advice to "Nancy" who asks:
"What kind of guy says "NO" to a friends with benefits offer?"
Maybe a smart one.
Off the cuff, I can think of three reasons your guy might reject an arrangement hinged on sex. My bet is, you're not going to like any of them.
1. You're psycho. Sure, girls "say" all the time they can handle sex without strings. Few actually can. For the most part, chicks aren't programmed that way, and guys know it. I could be wrong - though I'm hardly ever wrong - but I'd guess you made the offer because that's the only way you think you can get him. Maybe you're hoping your Kama Sutra skills will make him change his mind. It won't. And that's when you'll become psycho. Clingy. Needy. Desperate. He's saying "no" to bypass that messy scene. And who could blame him?
2. He's not single. And lo and behold, the guy's got morals. Sure, he's tempted but if he answers your midnight booty call, he runs the risk of girlfriend/spouse finding out (and they almost always do) or ruining a sure thing. Cheating statistics are up, but not by the guys with the scruples to say "No."
3. He's just not that into you. Maybe you thought that giant tattoo on your forehead was cute in college, but to this guy, it might be a warning beacon to stand back. Or maybe toothpicks aren't his thing. Whatever the case, you're physically not doing it for him - which means you won't be doing it with him, either.
Yeah, I know, love bites.