Perhaps you were looking at "top" tweets instead of "live" tweets. Top is the default

Probably a glitch from too much activity. These things can and do happen.

If twitter censored #ferguson, they'd get a lot of flak from feminists, so I don't see it plausible. Maybe a glitch?

Assume any centralized system will be censored, voat included now.

Ferguson is #1 on my trending list right now

If they did shut it down it's because shitlords were telling it like it is

In cases like this the censorship is not demanded or formal. Editors usually censor because they believe they are doing the world a favor by shaping public opinion toward what they believe to be the "correct" opinion.