I'm temporarily commuting with a laptop that has no WLAN device, so I've been using Google Reader's off-line mode for the last couple days, and I've noticed the following oddness.
I start out with a giant backlog of unread feeds, a la:
(Sorry for the quality of the screenshots in this post; if you click through to the original image on any of these, you should be able to see the folder counts clearly).
I synchronize to go off-line:
Once that's complete, all my folders show fewer unread items than before, such that my total unread drops from "1000+" to 580:
Such rapid progress! Until I go back on-line again:
And now I'm back to "1000+".
Anyone on the Reader team care to comment on this one?