I don't have a Kindle (yet) so I'm just interpreting what it seems like he said, but being able to create groupings that persist between sessions seems like a pretty standard organizational feature. Like in iTunes I can create various playlists to group my music however I want: playlists for parties, playlists for exercise, playlists for mellow background, whatever. I organize my bookshelves by grouping books according to general subjects (humor books, pop psychology books, books about programming, books about 3D animation, etc.) Would I be able to make groupings like that on the Kindle?