I just downloaded and tested Picasa 3.0 which google brought out in beta for the Mac. The program has an interesting UI and is nice and speedy. However, it does not colormanage. What the ...? Does Google realize that it is 2009? More than 15 years after color management was introduced to a main stream OS? Nowadays color management is a basic requirement for photographic apps. The absence of it makes Picasa useless for serious amateur or pro photographic work. Even worse, on uncalibrated Macs used by most consumers (i.e. the Picasa target audience), all colors will be wrong and images will have too low contrast making it even useless for amateurs. This is because out-of-the-box Macs come calibrated at the wrong gamma. Also, this means that if you have a laptop display, even if you calibrated and profiled it, you will always see the wrong colors. Therefore, my advice is to avoid this program like the plague until they fix it!
How Picasa displays two identical but for the color profile images (click for 100% image converted to sRGB from my monitor profile, so you can see what I see on my calibrated and profiled adobeRGB gamut display).
As you expect for color-stupid apps on a wide gamut display, the sRGB image is too saturated, and the prophotoRGB image looks green and too dark.
Both are quite far off as this image shows which is in sRGB for the web:
This is going to be even worse on a standard uncalibrated Apple laptop display, where everything is going to be severely desaturated and too low contrast.