Note: Belated news, I know.
Google has released another feature on its photo social networking site. Users of Picasa Web Albums can now be alerted about activity regarding not only their photo albums, but some activity in your friends as well.
(From Picasa Web Albums site) When people you have marked as favorites create new albums, upload more photos, or comment on your photos, we send you a summary of these activities to your email address at the interval you specify.
Users can adjust the frequency of the notifications by simply clicking on the settings link near the top...
...and adjusting their preference as seen below.
This should help users of Picasa's Web Albums to stay updated about what is happening on their site, although if someone desires to be notified more than once daily, then they may want to try subscribing to an album via RSS feed.