I think my main objection would be from the "what's the point?" camp. The diaries section is already set up for a LJ-type friends list, and any comments show up on the main page anyways.
That pretty much just leaves you with a MySpace style option, which seems to be mostly just for show. I just can't think of anything useful that would add (beyond possible drama). Other than having a list of people who I consider my friends (which, on a small site like this would only really serve to exclude people), what would a friends list do? The diary entries and messages are already set up in a friendly manner, I can have my frequent contacts readily accessible and highlighted on the recent user list, and it's not as if there are millions of users to sort through.
Then again, this objection could just come from my absolute hatred of MySpace ;-)