Picasa is a digital photo & video organizer which allows you to upload, edit and manage digital photos and videos. It also allow your friends and family to add photos and videos to your Picasa Web Album or vice versa. Once you signed into Picasa Web Album and visit someone Else's album, you will see 'Up arrow' icon located below the album. You can click that icon to add videos to your friends album. The owner of the album is responsible for all photos and videos uploaded to the album. You can delete the photos and videos which you have uploaded to someone else's album.
You can install PicBackMan's Picasa uploader for Mac from the website and start backing up photos and videos.