I think if we have to ask "Is that thing still around?" it isn't a good candidate to build something on top of. Best to make something new that works.
With dating sites you have the two giant problems you mentioned: people in your DB and pair-wise matching. I think huge time investment is a bit of an overstatement -- you can go with simple okcupid quiz-like matching.
But, in aggregate, the masses don't care about "good" or even "works." Yahoo Personals? A ton of people where you sort by distance. I think most of the dating sites are entirely sort-by-distance with some optional search filters. People don't know how to judge website product quality, so they use whatever either their friends use or comes up in a google search result.
While what you say might be true for first time customers, I would think the complexity of IRL dating would transfer to the world of online dating. Meaning that most simplistic sort by distance type measures should fail once people actually start attempting to use the product for more than one date.
With dating sites you have the two giant problems you mentioned: people in your DB and pair-wise matching. I think huge time investment is a bit of an overstatement -- you can go with simple okcupid quiz-like matching.
But, in aggregate, the masses don't care about "good" or even "works." Yahoo Personals? A ton of people where you sort by distance. I think most of the dating sites are entirely sort-by-distance with some optional search filters. People don't know how to judge website product quality, so they use whatever either their friends use or comes up in a google search result.
In short, http://www.google.com/trends/?q=yahoo+dating,+okcupid,+match...