Adobe does not seem to have tried very hard (if at all) to disable DRM-stripping. This would be harder for them than for Amazon (say), because they do not own most of the handheld devices that support mobile ADE. So it would take time to deploy a modified scheme. They can try to make it harder to discover the encryption key from Desktop ADE, and new versions have sometimes required an updated ineptkey.
Any vendor can change DRM at any time, so if you want DRM-free ebooks (even for archiving) it is a good idea to strip the DRM as soon as you get the ebook.