As an effort to ward off creeps or people who think that this is a dating site I think it would be awesome if we could implement some sort of an invitation where members can join if they are referred or they have to answer some questions and then maybe a moderator can review them before granting them access to join? It won't stop them but maybe if they actually have to put some thought into joining then wait for approval it may help?
Ribosom has had a great idea about having a community moderated system where members can vote on posts? I'm assuming a thumb ups and thumb downs system and if they have say 5 thumb down their post gets hidden or deleted? He might be able to elaborate more on his idea. Justfedup also had some great ideas.
To be complete honest I am not sure how to go about implementing any of these ideas but I've seen them on other sites (mostly pop up sales haha) so I know they're possible