Tom Doherty Associates, which published books under the Tor, Forge, Orb, Starscape, and Tor Teen imprints, has announced that it will begin publishing ebooks without DRM beginning in July. The change was apparently much-requested, perhaps because (as Tor put it) its audience is "a technically sophisticated bunch, and DRM is a constant annoyance to them." The publisher's books on current stores will move to DRM-free and the decision will also free up the company to sell books on stores that only feature DRM-free ebooks.
We're sure that other publishers (and especially Tor's parent company, McMillan) will be watching closely to see how Tor/Forge fares. As paidContent notes, there have been rumblings that larger publishing houses are considering making the switch. Presumably, the switch to DRM-free would be significantly less controversial than the switch to the agency model, but as it was in the music industry, we expect the publishing industry will take its time when it comes to dropping DRM.