I read somewhere that the writers rooms of Daily Show and Colbert rarely cross, at least day to day. I believe they deliberately keep them separate to keep them tonally unique, even though it sometimes results in both shows covering the same topic, and even occasionally making the same joke.

(Sorry for no source on that.)

I did some UX consulting for The Colbert Report that required me to research their entire writing and production workflow and my understanding is that the executive producers of the shows might check in with each other, but it's true that there's essentially no overlap, and there's no effort to coordinate topics.

Censorship doesn't require a conspiracy. It doesn't even require an explicit policy.

A lack of promotion here, a dinner-party snub there, and pretty soon everyone gets the message and falls in line.

I think part of it is due to the fact that Colbert has confirmed in the past that he is an active redditor, and on there SOPA has been a pretty popular topic.

Stewart on the other hand might just get his news from TV, which hasn't really covered it all that much

But Stewart has about 80 writers (I think) at least some of which I know to be techy. They must be keeping him aware.