The government got a little too ballsy--demanding owner identities of a Twitter account when no crime has occurred. If they don't have a problem doing that, imagine how many fucks they'll give when a crime has occurred.
Practice safe OPSEC.
Edit: if anybody cares for a legal analysis of what is happening, I formulated one:
Right now, this a dispute about the parameters of a government investigation, which is a Due Process issue. It becomes a free-speech issue when the government lays charges against someone as a penalty for a speech act. Twitter's citation of the first amendment is a smokescreen until those charges are laid. Anonymity isn't itself a first amendment right. More precisely, anonymity isn't a fundamental right that can be asserted against a government investigation that's properly conducted.
Twitter's real argument is that this government investigation is a fishing expedition, and not properly supported by a Due Process rationale. The government demand came in the form of an administrative summons. Not issued by a criminal investigator or an agency with regulatory authority over Twitter. That's pretty weak authority and Twitter doesn't have to resist by filing a lawsuit. But they filed and used a bunch of first amendment language as a way of communicating to their users that the company will go to the mat to protect users' anonymity.
Edit 2: DHS has withdrawn the request.
Twitter trying to finally get in the black and make some profit.