Stats on freemium services
zokiboy: To cheer things a bit, here are some higher numbers:Flickr: 5-10%
Ning: 3%
Online free-to-play games: up to 25% 
TurboTax Online: 70% (!!)Source: http://www.longtail.com/the_long_tail/2008/11/freemium-math-...My opinion: it depends on a lot of factors. From my experience without much effort you can get 1% users convert. But like I said there a lot of variables that can mess it up or down.