It'll be interesting to see if Snow Leopard's NSPurgeableData and related stuff moves to iPhone OS. (I gather Google's phone OS have something similar).

That'd let developers have cached data that the OS knows it can blow away safely if memory gets low. The app then just regenerates the cache when necessary.

If iPhone OS could look around running processes for purgeable data, it could avoid or postpone killing apps outright. That would only be necessary if purging wasn't sufficient.

In fact, this seems a lot more useful on a swap-free phone than on OS X itself.