When I last ran Picasa (Sunset version), I noticed that it did thumbnails for my videos like that. It was new to me - but that's because I would not have noticed when they introduced that as I usually only use Picasa for still image management (at which, it is excellent). Quite useful, I thought. Not sure if it does it for all video types though.
CORRECTION: Oops, sorry. Disregard what I wrote above. I was mistaken. I just went and quickly checked Picasa. It only does one thumbnail for each video - not several. The one it does may vary though - i.e., not always the same. Have not exhaustively tested it.