They took over the most popular subreddits as AskReddit or IAmA. They also ban subreddits/users and remove posts that can make a bad name for reddit in the media. Both from these brand subreddits and from the whole site.
Considering they have a strict AUP they've been remarkably tolerant in what they ban. A few blatantly illegal sub reddits; some sub reddits with borderline illegal content; and some harassment only sub reddits.