Abuse of the karma system is a well-known problem on LessWrong, which the admins appear to have decided not to do anything about.
Update: actually, it appears Eliezer has looked into this and not been able to find any evidence of mass-downvoting.
It's happened to me again. At one point I lost about 20 karma in a few hours. Now it seems everything I post gets voted down. At an estimated loss of 30 karma per week, I'll end up being forced off the site by August.
Another month has passed and here is a new rationality quotes thread. The usual rules are: