(yeah - I know that's not as true nowadays as it was at the beginning of y2k, but I'm trying to make a point here...)
I've always thought the distributed social site concept had room for both those people who want to run things themselves and for service providers. Kind of like wordpress.
It's possible that in a couple of months Diaspora will look a lot less like a Great White Hope. We will see.
That said, I'll only use Diaspora for myself, but that's based on personal preference.
I know Ruby like the back of my hand and am comfortable with Rails. Also, my site's built in Rails, so Diaspora will probably integrate nicely.
In other words, it's software for anyone who wants to run their own facebook-like site. Except that all the sites running it connect to each other.
Once it's out of beta, most users will just go to a sign up page of any number of nodes out there (I think there's like 50 out there already? I'm not sure)
Typical facebook users are not early adopters. None of these projects are even close to targeting typical facebook users yet.