The old debate: one night stands
This is a comment on Mikey's post, which was in turn inspired by Dan's. Which is what blogging is all about, really: conversations held with really long pauses, so you can actually think about what you want to say, and state it eloquently (or more eloquently than if you'd had 2 seconds to come up with it).
Of course no relationship ever came from a one-night stand of anonymous sex, because all the ones that became relationships no longer classify their first time as anonymous, nor was it a one-night stand. It's like saying no sunken ship ever reached port*.
I think it's probably true to say that most people currently in a relationship got to know each other a bit before having sex, but I think that's a false correlation. Most people are quite intimidated by sex, so most people get to know each other before they feel comfortable enough to have sex. So although people who had sex very quickly and are in stable relationships are in the minority, I think this is only because people who are self-confident enough** to have sex very quickly are in the minority in general.
Of course, only a subset of the people you find attractive enough to have sex with will you also find compatible enough to date, so if you have sex first you will end up sleeping with a lot of incompatible people. But if you take the other route, then you will end up spending a lot of time getting to know people who are sexually incompatible with you, and the two are of at least comparable importance. So who's to say which route is better? You might argue that emotional/intellectual compatiblity is more heavily weighted than sexual compatiblity, and so narrowing people down on that criterion should be done first. But sex being quicker than getting to know someone, one might argue that the sex-first method is more time-efficient, since no matter how much you like someone, a relationship will be nearly impossible if you cannot be physically intimate.
Having alternated between these two routes for four years now and still being single (with no relationship making it past the apparently crucial three-month mark) I can't say I have had marked success using either approach. But nor have I found one approach better or notably more successful than the other -- no matter how they started, they ended.
* Yes, I'm aware that in a few cases sunken ships have reached port. Bugger off now.
** The ability to get people into bed quickly is entirely based on confidence, not attractiveness. I can cite numerous examples, more than one of whom I've slept with myself.