Maybe as a comparison to Twitter? Clearly Plurk is not as well-known, but in a lot of ways it's functionally better.

Guy took an HCI class and it was one of his favorites at UE

I think that would be interesting study. Plurk, I think, has a different functionality than Twitter

Twitter seems to be mostly interacting with people you don't know and seems to be a more political platform (political in the more technical sense of the word)

whereas Plurk seems to be more about being able to interact with people you know

Very true. My plan is to set up a test group of people who interact with each other in real life (probably the people who work for me at my libraries) and have them try Plurk for a week or two.

Then I'll interview them to find out how they felt about the various features.

I'm thinking about having them demonstrate certain tasks for me as well, to see how user-friendly Plurk is versus Twitter.

they already be familar with Twitter?

like it would be great if you could get a group that didn't really use either one

That's true. The group I'm planning to use (the employees at my two libraries) are a mixed group; some have twitter and some don't.