Some random person on Picasa shared an album with me. I have no idea who they are or why they shared with me. Some random travel pictures of Malaysia or something. But it was irritating to have to see it in “Favorites Activity” every time I went into my own albums.
Google doesn’t provide a direct way from the activity list to remove someone. The process to remove it is to click the shared link and go to the other person’s gallery. Add them as a Favorite using the link on their album.
Then when you go back to your own People/Favorites tab, and click the “List” link in the top right corner, there are checkboxes to stop getting updates from them or to remove them outright.