+1 to everything justaagirl said, with two more points:
(1) Don't write off Airbnb, but choose properties that have Superhosts. As mentioned above, even one cancellation means a Superhost will lost the status for a full year, which is a painful thing. (I'm a Superhost myself and I am very conscious of maintaining it.)
(2) It's not the host that kept your money for all those months, so although you have every right to be pissed off about the cancellation, that's one thing you can't accuse the host of. We get paid only when the stay occurs. Airbnb keeps the float.
I agree with the suggestion to contact Airbnb and complain. They are still a new enough company, and concerned enough about their reputation, that they will give you some kind of benefit to make you feel better. It will likely be a credit for a future stay. I got this once for both myself and one of my guests when Airbnb screwed up her registration process and caused serious hassles for both of us in booking her stay.