I'm the former owner/operator of ww.com, in its day a pretty large video streaming community, think 'twitch' but many years earlier. We had fairly regular contact with the police to ensure that our members were operating within the law, and some of them repeatedly decided to test where the line was. As responsible operator of a large web property you are an extension of society and society has - fairly universally - come to the conclusion that having a police force is both useful and necessary. As a forum operator you can choose to go head-to-head with the authorities or you can choose to work with them, we - just like Twitter - chose to do the latter because we believed that this was in everybody's best interest.
On occasion it wasn't the authorities initiating the request but us because we came upon acts and or proof of crimes to despicable to relate here and they were uniformly courteous and acted with surprising speed against the perpetrators. Law enforcement and corporations have regular contact, anybody that believes that this is not the case at the level of a Twitter or a Facebook is utterly naive.