I don't realistically think they can "run" an MMO unless they partner up with one of the mega-publishers, who can maybe handle some of the customer service, technical service and server hosting issues, or help pay for it. But at that point, Runic would lose its independence, which is what its whole appeal is based on; or it would have to double, triple, etc. in size and become something very different than what Runic wanted to be (i.e, a big bureacracy with humongous staffs and development groups).
I'm sure they already knew all that. I don't blame them for getting cold feet, if that's what this is, but CeeKay's right (stop the presses!

), imho -- maybe they shouldn't have babbled about MMO plans if they weren't truly committed to the idea.
imho, it'd be more realistic to do some sort of battle.net-type secure server for Torchlight 2. That isn't by any means cheap to do, but I think (perhaps with some Kickstarter funding boost or something) it might be reasonable for Runic to do without expanding the company massively or losing its independence to a big publisher.