Speaking of paid email services, there's no way to subscribe to Mobile Me with an in-app purchase. If Apple cared about fairly enforcing the rules, they'd yank iDisk and Find My iPhone until in-app subscription to Mobile Me was added.
A small quibble: the Find My iPhone service is free for all iPhone4 (maybe all?) owners. That is a good point though, although the rule doesn't come into effect until June.
