The problem still seems to be around. Yesterday I synced my Glo for the first time since Thursday, and I suddenly had 288 pages of shelves. When I looked in the database, the were over 2000 rows in the Shelf table. The creation and last modified dates went back to July last year, which was the same as the last time this happened. The fix was to delete all the rows from before my last factory reset. The sync after that didn't recreate the extra shelves. I checked the database for the desktop app and found the same thing. I haven't checked the Touch yet.
@Corpsegoddess: The dates Peter and I are talking about are in the database. They don't display on the shelf list. The creation date is displayed on the "Add to Shelf" screen.