I just figured they wouldn't appreciate it because it 'harvests' data from facebook... in the same way they didn't like that firefox extension that converted the email address images into plain text.
It's a bookmarklet though, which means it's all client side javascript, which will make it pretty hard to block. It's basically a greasemonkey extension, and if you look at all the GM extensions available on userscripts.org, there are some that do pretty crazy things and are usually updated on the same day the site owner changes something that causes the script to break.