Twitter suggestion

Here's a set of functionality that would dramatically improve Twitter's usefulness:

1. The ability to group people you follow and assign those groups priorities. So, for example, friends might be priority one, casual acquaintances priority two, and people you follow for fun- bloggers, say- category three. Or something like that.
2. A sliding scale at the top of the Twitter window that allows you to dynamically raise or narrow the scope of your Twitter message stream to include only category one messages, or category one and two, or all three.

You get the idea. A system like this would make it easy to quickly expand the scope of people you follow without constraining your ability to focus on the content you want to focus on, when you want to focus on it.