In a phrase; "Is this new?"
I managed to intertwine a half dozen meetings with SES London and as a result I've been too busy to keep up with my RSS. I decided just to 'catch up' on all the items from The Register by just marking them as read.
This is new to me. Normally Google Reader does whatever I want and without questioning my orders. I do see the need, I suppose, for a "are you sure" on such as large group action... but I'm certainly not used to "are you sure" requests from Google. In fact, a number of Google Engineers have blogged about the failture of the "are you sure" approach and that an "undo" option is far superior.