[fjtorres]

Adobe DRM is probably safe; after all, it is supported by one of those feuding "big brands". And it is the DRM of choice of the anything-but-Amazon camp.

Ebookstores that rely on Adobe DRM and servers, though?
Those are at some risk.

Basically, the entire Kindle market gets its DRM'ed content from Amazon.

The Adobe DRM readers, however, are an open competition between B&N, Kobo/Borders, Sony, Fictionwise, and a zillion "national champion" regional stores. On paper, all devices and ebookstores are supposed to be equal under Adobe. The reality, though, is that Nook is more equal: Nook's Adobe support is one-way; it supports plain-vanilla Adobe DRM but their DRM is currently only available on Nook hardware and likely will never be available at competitor bookstores. And, unlike Adobe, B&N is actively porting their reader software to smartphones and tablets.

And, because Nooks come hardwired to the B&N store they'll have preferential access to Nook buyers. Other bookstores will have to rely on PC-based sales to get to Nook buyers.

So, the way it works for now is the largest single block (Kindle) is off-limits to vanilla Adobe bookstores and the single-largest block has a strong incentive to go with B&N. Its not much of an issue right this minute because B&N hasn't gotten their act in gear outside the US but once they get their regional right story straight there is serious danger for the other Adobe Adept bookstores. Especially if B&N DRM support shows up on second-tier readers.

And, of course, iBooks doesn't have much of a presence but over time they might amount to another big player.

For all that buyers gripe (and rightfully so) about regional rights on ebooks, those regional rights are the best hope the regional ebookstores have to survive.