I'm surprised that I'm the only one who noticed this.
Adobe just announced today that the latest update of the RM SDK is now available to all developers. This means that finally ereader manufacturers ebookstores besides B&N can use sell the password protected Epub:
Today, Adobe has released an update to our Digital Publishing Solution for eBooks, including Content Server 4.1 and Reader Mobile 9.2 SDK. With these updates, book distributors can enable “social” password-based content protection as well as text-to-speech accessibility support for eBooks. In addition, Reader Mobile SDK includes a number of rendering, font, and color management enhancements.
So, just under a year from the day when those idiots split the Epub market in two, they released the code so it could come together again. Smooth.
Unfortunately it's too late now; there's already too many current ereaders that will never support the new DRM, and that's going to block most ebookstores from updating, which will discourage manufacturers from updating their existing models.
And don't forget that Epub 3.0 is in the pipeline. The details aren't set yet, but it looks like it will be a huge shift from the current 2.1. Everyone knows it's coming, so there's a good chance they'll avoid this update in anticipation of the next one a year to 18 months down the line. (Or do I have my details wrong?)