One Idea I've thought in this area solves the question you were asking about, what activity/excuse the users have to come meet?
Well instead of that being a question for you, make it for the users... Users can enter in activities they want to do? (may it be grab some coffee, see a new show, bird watching, even slightly non dating things like jogging or carpooling, etc). It'd be something like Craiglist, but more focus and non chaotic on this aspect of person-person activities... Now the site would do is match up these based on relatedness of activities the person would like to do.
Well instead of that being a question for you, make it for the users... Users can enter in activities they want to do? (may it be grab some coffee, see a new show, bird watching, even slightly non dating things like jogging or carpooling, etc). It'd be something like Craiglist, but more focus and non chaotic on this aspect of person-person activities... Now the site would do is match up these based on relatedness of activities the person would like to do.