(Reposting a comment I left over there, too.)
I applaud the idea, but frankly I suspect that even if Hachette did pull DRM from all its books, and the other publishers too, it probably wouldn't help.
Dirty little secret: DRM isn't the real Amazon customer lock-in. Oh, sure, it is in theory, but there's a considerable difference between theory and practice. Honestly, anyone tech-savvy enough for DRM to be an impediment to their switching providers is also tech-savvy enough to crack it and back those books up.
You know what the real Amazon customer lock-in is? User-friendliness and convenience.
People buy Kindle because Kindle makes buying e-books from Amazon simple. And they keep buying e-books from Amazon because…well, Kindle makes buying e-books from Amazon simple. When my Mom wanted to sideload Project Gutenberg e-books onto her own Kindle, I had to talk her through it over the phone, and it took a half hour. And you know who most Kindle owners are? People's Moms and Dads, Grandmas and Grandpas. I would venture to guess that the vast majority of Amazon's customers wouldn't know what to do with a DRM-free file if it nipped them in the arse.
Consider the case of Baen, who sold e-books DRM-free, in Kindle-compatible Mobipocket format, for well over a decade. They provided clear instructions for how to sideload them, even put a web form on their page so people could simply fill in their Kindle e-mail address and send their books directly to their reader. And yet, Baen still got complaint after complaint that their books "aren't on Kindle," because anything more complicated than clicking the "buy" link in Amazon's store was too complicated for them to understand.
Finally it got to the point where Baen realized it was leaving more money on the table than it would cost them to give in, and they made sweeping changes to their e-book store (disgruntling many long-time customers) for the sake of getting their books into Amazon (and the other major stores).
Mark my words: if every major publisher stopped using DRM tomorrow, Amazon would still have a lock on the e-book market for years to come.