Aha, but of course, these services and time wasters will just adapt to have no ads. Essentially, I fear that all apps will take the approach of being excellent

Aha, but of course, these services and time wasters will just adapt to have no ads. Essentially, I fear that all apps will take the approach of being excellent time wasters or services (because that's what they're being paid for), and killing all the truly great apps that that have around 20 people using them, yet cost around $7. And are not as addictive as these time wasters. Some apps try to minimize the time spent in their apps (a losing strategy in this new economy) because people pay them for a fast, frictionless service (think Drafts), but put less time into them than a browser or addictive game.