[nemo44x]

The law specifically says they are not liable. Either is someone who perpetuates the info by retweeting, for instance.

However if you modify the retweet at all then you too can be held liable.

[lightedman]

The law states they are not liable as long as they do not demonstrate effective control on what happens with their service. They have demonstrated that they do indeed control what happens on their service, and what gets posted there.