Addition: I don't use my Adobe-ID for anything else. (Previously, I used it to activate my student license for Photoshop, but I've moved away to GIMP, as it has improved enough for my purposes.)
I assume that, if I download an ASCM-file from Kobo (or somewhere else), that I can download the book using ADE on any computer, authorised by any e-mail address. It must be, because the e-mail address I use at Kobo is not the same as my Adobe-ID (anymore), and this still works.
Does this mean that if I run out of authorisations, I could just create another Adobe-ID, and use that to download books, and then de-DRM them? If so, then there basically isn't any problem. I have my own webspace/e-mail domain, and I can create addresses like
adobe_0001@mydomain.com by the thousands if I need to. After authorisations run out, I just delete the address and abandon the ID, create a new address and a new ID, and just leave the old ones to rot forever in Adobe's database, without even a name filled out or anything...
As I de-DRM all my books at the moment of purchase, this means that not being able to read protected material is a moot point. Obviously, for people playing completely by the DRM-"rules", this would not be an option.
Oh, how we love DRM... if a "normal" user gets into trouble, he's really down the drain.