So, the FBI is asking for IPs used to comment in two posts whose authors later committed acts of terrorism. Doesn't surprise me, I had thought they would have done this already.
I'm surprised there's an actual search warrant. I would think these websites get so many requests for IPs that there's not some way the websites hand it over without a warrant.
Websites in the US (which doesn't, I believe, include this one) have to follow the Stored Communications Act, which specifically forbids disclosing customer information just because someone asked.