=== How easy is it to set up a system similar to EduBlog ===
You can, but it’s not easy. Dedicated servers, multiple databases, a team of experts – coders, programmers, tech support personnel. etc. etc. etc. It’s akin to WordPress.com http://edublogs.org/why-edublogs/
Well, I do really like Edublogs, but there are many options I would like to tweak. I do have a lot of WordPress experience, but not that much MultiSite/BP experience. I was planning on using WPMU Dev Premium.
Create a network and go learn as much as you can before you open up a service for free and for pay where users will expect no downtime and top-notch support, among many other demands – reasonable or not Good luck.