Every time you see a big, free, ad-supported or VC funded startup with millions of users, just know that there is probably a place for a paid application that i

Every time you see a big, free, ad-supported or VC funded startup with millions of users, just know that there is probably a place for a paid application that is basically the same app only charging money. Even for social networks and things, people will gladly pay money for value you provide. The problem is that it's not the kind of thing that VC's will get as excited about, because unless you can grow into many millions of dollars of revenue fast, it's probably not an interesting way to turn over their money. So, GMail, Tumblr, Twitter, Facebook, even something like Groupon could exist as a successful paid app with a one time or recurring revenue stream.