If love don't cost a thing, why are online dating sites charging so many fees? The wave of the future, perhaps: free Internet dating. In April, craigslist saw 2.6 million personal ads posted, up from only 970,000 two years ago. Plentyoffish.com, a free dating site that was launched in 2003, now brings in 200,000 U.S. users a day—and $5 million to $10 million in advertising a year—according to its founder, Markus Frind, who runs the site by himself. "I think all the paid sites are going to go away," he says.Even Match.com is offering discounts to subscribers: six months free, if you don't find Prince (or Princess) Charming in the first six months. While the online-dating industry has been enormously successful so far—the market grew 10 percent last year to $649 million—the number of subscribers is expected to flatten after 2009, reports Jupiter Research. "The growth is not what it was before," says senior analyst David Card. How heartbreaking.