Google claims no ownership or control over any Content submitted, posted or displayed by you on or through Picasa Web Albums. You or a third party licensor, as appropriate, retain all patent, trademark and copyright to any Content you submit, post or display on or through Picasa Web Albums and you are responsible for protecting those rights, as appropriate. By submitting, posting or displaying Content on or through Picasa Web Albums, you grant Google a worldwide, non-exclusive, royalty-free license to reproduce, adapt, distribute and publish such Content through Picasa Web Albums, including RSS or other content feeds offered through Picasa Web Albums, and other Google services. In addition, by submitting, posting or displaying Content which is intended to be available to the general public, you grant Google a worldwide, non-exclusive, royalty-free license to reproduce, adapt, distribute and publish such Content for the purpose of displaying, distributing and promoting Google services. Google will discontinue this licensed use within a commercially reasonable period after such Content is removed from Picasa Web Albums. Google reserves the right to refuse to accept, post, display or transmit any Content in its sole discretion.Be sure to check out the terms if you plan on uploading images.
Personally, since I upload thousands of images each year I prefer to use a "pro" service like Flickr which provides me with complete ownership etc... be wary of free services like youtube, picassa etc... as you may be giving up some form of ownership to your images and video. For more info see the Google/Picasa terms at http://picasa.google.com/intl/en_US/web/tos.html