Caution is the rule
After reading all this I'd be very cautious about book purchases.
It appears Sony and BN and Adobe all have DIFFERENT copy protection schemes. They may not be interchangeable or crackable.
I just installed the new Adobe 1.7 for reading DRM protected PDF books. It would not read files I had moved from an older PC 4 years ago. The message stated that all their DRM PDF books are LINKED to a specific PC.
I did download a free sample of a BN book yesterday and Sony 3.1 could read it. Today I downloaded a new sample of a BN book and Sony 3.1 could NOT read it. It appears the DRM mechanism is EVOLVING.
My solution is to use BN only for the free samples to try the book and then only purchase the books from Sony. These DRM ePubs are completely different than the free ePubs obtained elsewhere.
I have a Sony PRS 505 now but soon will have the Sony PRS 900 and get rid of the PRS 505. We will just have to pay higher prices at Sony to be sure we can read these books.
My present BBeB files can all be read by Sony 3.1. However, some are now unavailable for download. I went through 10 books on my wish list at Sony and removed them first and then reinstated them. I received no warining on those of not being available for download.