[necrecious]

So essentially blog categories?

This feature is only useful for a very minor audience. Most people don't create a lot of content, and won't bother tagging their short tweet/status.

Power users who do write a lot should already have blogs like the one the author is using.

[joshuahedlund]

Most people don't create a lot of content, and won't bother tagging their short tweet/status

This is a good point, but couldn't that also be said for the existing way Circles work? I think some form of the reverse would be better for power users without affecting the casual users.