My Macbook battery icon in the menubar shows that the battery is missing - it displays only an "X". Too bad!
I've tried resetting the PRAM as well as the PMU, with no results. This thread mentions a mainboard issue: http://www.mac-forums.com/forums/showthread.php?p=429081
Maybe that is the problem.
This is actually a major issue, because the Macbook uses the oh-so-convenient Magsafe power cable, which is a bad thing when you have no battery. I guess I'll have to super glue it on or something. Aha - found this page which promises a replacement battery:
Just finished up at the "Genius Bar" and left with a free replacement battery. The Apple Service Representative at first said that since my Mac was out of warranty, I'd have to buy a battery, so I'm glad I printed out the page that said in clear terminology that Macs out of warranty were included in the replacement offer. I'm glad, and a little surprised, that they lived up to their promise.