It depends what you want really, most of the points people have been making are great. This is how I work:
If I (or the said person in a relationship with me) is together, then no, I don't like either being a 'slut' or sleeping around because not being faithful isn't nice, having it been done to me in the past, I can safely say I don't want it happening again.
But, if you're single and ready to mingle, then why not, you only live once, sleep with who you want, when you want, where you want in what position you want. I'll admit it, if I'm not in a relationship, I do it. It's great. It's what makes the world go around (ok, I'm joking about this, but it get's my point across).
Also, the whole "Slut" thing, it could be taken offensively, well, not from me, if I was called a slut, I'd be well made up, at least it means you CAN actually get someone..