I was going through my RSS backlog and ran across this blog entry on Gamasutra. Ethan Levy, a monetization design consultant, makes an excellent point about in app purchases.
It’’s not just enough to have them in the game, but you have to make them present. Let the user know about them, and why they might like to do so, without breaking the game flow or interrupting their experience.
It’’s a short article, read it for yourself: