BMP files actually support full 32 bit colors, and even has an Alpha channel, much like PNG files, its Jpeg that doesn't support True 32bit colors, mainly because it uses compression. This however, is not noticable by the naked eye.
More information on BMP files can be found here:
http://en.wikipedia.org/wiki/Windows_bitmap
I applaud this move, becuase BMP files use too much Bandwidth, and are apain to download, even on high speed.