Because of its low ratings last year, it's really a wonder that "Dollhouse" got a second season from Fox at all. So this cancelation shouldn't be a big surprise. A disappointment, certainly. But not a surprise.
"Dollhouse" has a small but devoted following, mostly people who dig anything show creator Joss Whedon touches ("Buffy the Vampire Slayer," "Firefly," "Dr. Horrible's Sing-Along Blog," "Angel"). It's a good show, but for whatever reason, just never caught on.
Fox is allowing the show to finish out it's 13-episode run. Whedon is currently filming episode #11, so hopefully he'll be able to bring closure to all twelve of the show's fans. The finale is tentatively scheduled for January 22.