First off (like someone said) it's an online social network - there will be lots of creeps by default. But CS helps weed them out by encouraging references and friends. It's not perfect, but it's a good indicator of behavior.
Second, the whole point of CS is for (mainly) adults to socialize in foreign places. If my theory that the users are at least 50% single is correct, hookups are going to happen. CS even makes it easier by encouraging like-minded people to meet each other, and spend several days together.
Third, local communities that meet regularly form a kind of peer social network that will lead to people hooking up. That's any local community, be it an indie music scene, a foodie group, whatever. CSers who tend to get together locally are (imho) lonely and want to have fun with other people, so hooking up is more of an eventuality than a possibility.
I agree with you that very few (if any) of my CS meetings led to real friendship, but I didn't get into it to make new friends. I just like travel and meeting people.