What exactly are tag profiles in SP 2010? I can't seem to find the right information on this. What is the benefit of it?
Tag profile is used by Managed Metadata service as a landing page for a keyword/term.
It means items that are tagged in SharePoint each get a My Site-type profile page of their own. It’s basically an index of that tag, everything that's tagged with the term, be it pages, documents, blog posts, whatever. You can read and leave comments, see which users have used the tag, follow the tag as an interest.