Picasa 2's "Timeline" feature

As a sometimes interface designer, I am perplexed by the timeline tool.

The timeline is a series of "piles" of photos -- but how did they get that way? Does each pile correspond to one folder on my drive? One date? How many things are in the pile? How "big" is the pile? They're somewhat inscrutable objects, because they give me no information whatsoever.

There's no way for me to look inside the piles themselves and review the pictures there, in-place, synchronously. When I double-click one, I have to watch . . . a slideshow. (How often could that be the desirable behavior? When I open my email inbox, would I want a slideshow of my emails?)

Behind the timeline, there is a desaturated picture, presumably a sort of representative of an "era" in my picture library timeline. Is there a representative for each pile? Not exactly; it seems hard to predict when that picture will actually change. How is the representative picture chosen? Don't know. It seems like there could easy be more than one -- how about four, tiled together? There could also be a few sample words -- important-seeming people and place names taken from my photo's file names or folder names, for example, helping me to get some context for the era of photos that I'm looking at. Or just some filenames.

I'm thrilled that Google is letting fun, creative interface design work see the light of day in a major product like Picasa, but I must say that this particular widget needed a little more Google-style attention to detail.