In theory, there is a setting to stop people from downloading your photos. But, in practice, it is now possible to protect your photos and videos of your Picasa Web Albums from being downloaded by others. You can limit the usability of your photos and videos by uploading them in a limited resolution which is sufficient for web usage, but not sufficient for printing. Picasa Web Albums allows you to control who can see your albums. It gives you 3 options i.e "Public", "Limited, anyone with the link" and "Only you".