In reading this - it makes you consider what happens when having a marketing group becomes less important.... Get your fanatical customers to market your product for you and reward them by giving it to them for free.
But I think there is something even more important to notice about Tap Tap's success. When Seth Godin released his first marketing book, Permission Marketing, he gave away the first four chapters for free via pdf to over 150,000 people. It generated a lot of buzz about the book and was a big factor in the book's success when it eventually became available in hardback. So when he followed up with Unleashing The Ideavirus, he went one step further. He gave away the entire book for free in pdf (it still is available free). Seth says that over 2mm copies were given away. And yet when the book was published in hardback it went to #5 on Amazon. It was a demonstration of the very tactics Seth was evangelizing in the Ideavirus book. Seth asserted that by giving away your product early to your greatest fans who will do more work and put up with a less than optimal experience, you prime the pump for the mass market. That's because your early fans will spread the ideavirus and market the book for you.
Tapulous did the same thing with Tap Tap Revenge. The game was first made available for the iPhone at the start of this year. But the only people who could play it were people with phones that were jailbroken. So it's audience was small, but fanatical. These were the early iPhone app adopters, the ones who would work harder and put up with a less than optimal experience. But now that everyone can play Tap Tap, the early adopters are telling everyone else how great it is.