This from a reader Mike:

"I own a 17inch Macbook pro (not core 2 duo) and I recently had one of the cells on my battery balloon to about twice the normal size. The cell forced the cover of the battery to pop off. I took the battery to the Apple store today to have it replaced and they seemed in a hurry to get it out of public view so as my "genius" went to get the replacement I took some photos...The Apple nerds said they had never seen anything like it."
Macbook Pro Batteries Are Inflating?But what about our other readers? Is anyone else experiencing inflating Macbook Pro batteries? – Mark Wilson
Thanks Mike!