Google working on offline Gmail client?

There are lots of rumors floating around at the moment about Google possibly working on a client-side version of their super-popular Gmail e-mail service. The standalone program would allow users to store their emails on their own computer and work on email offline, even when not connected to the web.

While I wouldn't put this past Google, it doesn't really make a ton of sense to me. Sure, it's convenient to be able to write your emails offline, I suppose, but you can use plenty of standalone clients with Gmail already. Google probably wouldn't bring much new to the marketplace, and I don't see a huge benefit to them investing the man-hours into creating a piece of software that they'd then have to support on many different computers. It seems to me that they should just stick with the online client, but I know better than to question the wisdom of the great G.