Few months ago, .05% of documents hosted Google Docs which were private have been set to public because of a bug
http://troogle.wordpress.com/2009/03/07/google-privacy-blunder-shares-your-docs-without-permission/

Today, same problem with Picasa Web Albums, as reported by a reader of Zorgloob.com :

<< Dear Picasa Web Albums user,

We wanted to let you know about a recent issue with your Picasa Web Albums account. As a result of a bug in our email notification system, some links and titles to unlisted albums and photos in your account may have been inadvertently sent to a limited set of other users – those listed in your account as "Fans". This involved unlisted photos only – no 'sign-in-required to view' photos were involved. We fixed the issue within hours of identifying the problem.

To help remedy this bug, we have reset the unique web addresses for all albums that may have been affected. This helps ensure that these albums are inaccessible to anyone that attempts to view them using the outdated web address. If you would like to re-share these albums, please do so by clicking the "Share" button while viewing the album.

We're sorry for the trouble this may have caused. Although this issue only affected about 0.05% of Picasa Web Albums users, we want to assure you that we have treated this issue with the highest priority.

The Picasa Team

Some photos from the following unlisted albums may have been affected, so they have had their web addresses reset:

XXXXX
YYYYY
ZZZZZZ {albums names removed by TOMHTML}

---

You have received this mandatory email service announcement to update you about important changes to your Picasa Web Albums account.

Google Inc. 1600 Amphitheatre Parkway Mountain View, CA 94043
>>

What do you think?

Anyway, the fix has created a bug for ALL other users
http://www.google.com/support/forum/p/Picasa/thread?tid=2e6dd2bfbf22342a&hl=en