Panasonic is facing some issues with notebook batteries, akin to the issues that Sony and Dell are facing on much larger scales. With concerns about overheating, Panasonic will be recalling 6,000 notebook batteries. While the battery itself coming stock isn't a concern, it seems that rough impact or other damage can result in a spring coming loose or falling off, which can result in overheating:

The Matsushita spokesman said that when a notebook PC using the battery in question had been accidentally dropped on the floor or suffered any other strong impact, there was a chance that a tiny metal spring used in the battery pack could fall off on to battery cells, causing overheating.
Luckily, there haven't been reports or concerns over injury, and Panasonic is choosing to err on the side of caution.