The same issue could occur at Amazon, I'd imagine. Although you can authorise 6 copies of most DRM content, a single Kindle account tracks this. So, in a two Kindle account household you'd have to swap devices depending on the account. Erm, just like you do with a paperback.
I maintain one Kindle account but have two Kindles so the hubby can read on his own -- and we manage one collection of books. I am hoping to use the identical strategy when I get the wifi Kobo in a week or so. I assume that works with both the desktop and the ADE software?
And, as taming pointed out, the DRM is doing its job. I am fully supportive of that. Kobo's job is to ensure the user experience is as simple and transparent as possible.