Beware! Your lovely family photos on Picasa Web Album might appear in Google Image search results. Google has recently changed its policy and to include public albums in Google Image Search. Here's the official word:
Integration with Google image search resultsGet more exposure for the public albums you're currently sharing on Picasa Community Search. Now, public albums from users with 'Public Search' enabled may also be included in Google image search results.
So if you don't want somebody else to see your private photos, better unlist them.