Thus why you should only buy ebooks where you get easily transferrable formats, like unencumbered PDF or ePub. I'm a big fan of O'Reilly's multi-format approach. This is the correct end-run around proprietary stores. Regarding this issue in particular, I don't see the problem with Amazon and others kicking their users out to Safari to do purchases, and thus as the purchase wouldn't happen "in app" it wouldn't be cove…
But is there any big player in the ebook market which comes even close to Amazon (collection-wise) and sells non-DRMed books/PDFs? From what I've seen there are no viable alternatives for non technical reading... (and no, shopping at several small publishers' websites is not a viable alternative)