This isn't a theoretical, and it's sadly not limited to the iPad. I've purchased the Apple suite of office programs (Pages, Numbers, Keynote) and I can't install them without updating to the latest version of Mac OS X. That's OK for me, but it's been a huge PITA for the non-profit I work with, which is always struggling to get working computers, let alone modern ones. Because they can't install Lion on their computers, software we'd bought for them simply won't be re-installable if I have to wipe the system clean for some reason.

I was fed up with Android bloatware enough to finally switch to iOS a few weeks ago, but the lock-in on both platforms (non-stock Android + iOS) is beyond aggravating and feels more like a shakedown at some points.