http://en.support.wordpress.com/avatars/blavatars/ indicates that a blavatar will be visible "across WordPress.com." This seems to indicate that users can have only one blavatar across all WordPress.com blogs. A more accurate statement might be that a blavatar will be visible on a variety of WordPress.com pages.
I have found the extant statement confusing. Unfortunately, I am not finding a way to convey this simple feedback to WordPress.com directly. Suggestions are welcome.
Blog url: http://phdatiu.wordpress.com/