Any venue in which lots of single people invest time and energy in something that interests them can provide the thickness needed for an effective mating market. You can get a date by being an active Yelp reviewer*, and, it turns out, World of Warcraft isn't bad either, as Stephanie Rosenbloom reports in the NY Times: It’s Love at First Kill
" With more than 12 million subscribers, World of Warcraft is one of the most popular games of its kind in the world (others include EverQuest, Aion, Guild Wars). That’s a sizable dating pool. Match.com, by way of comparison, has fewer than 2 million subscribers."
*My new HBS colleague Mike Luca has studied Yelp, including (in passing) the way that they create a social network for their most active reviewers.