> I definitely agree that I do not want extremist groups to grow and become even more of a 'thing' in the US. However, I do not know if I am OK with stripping people of their 4th amendment rights just because they have been 'associated' with a terrorist group (or visited a terrorist group's website...) That's a dangerous path.

Me neither. I'm about as gung-ho about personal privacy as it gets.

I'm also practically minded and understand the difference between things that are and are not in your control. The log of whether I visit a particular website on my computer is under my control. You need a warrant for that. But that same website has it's own logs and I know that I have no privacy or 4th amendment protections[1]. Now they can demand a warrant from the government for their records, but they can also give it willingly. Either way it's up to them, not me.

> I also still fail to see how the information taken from Dreamhost would help them track somebody who committed a crime. What, are they going to subpoena everyone's ISPs to find out who every single person is, then arrest them and see if they happen to be someone who committed a crime? That's wrong. What am I missing here?

I can imagine intersecting whatever lists they get from here with other similar data. Maybe mixing in the geolocation of the anonymous user's IP addresses. Combine in email address to name lookups. Without knowing what else they have it's all conjecture, but I'd imagine they've got something to tie it against.

> How could this be used in any way except to build a list of 'potential terrorists' in some 3 letter org's database?

I wouldn't be surprised if they're doing that and bet most three letter agencies have multiple lists of potential undesirables on which they want to keep tabs. I mean that is their job right? You don't just want the FBI to arrest people after they commit the crime, it'd be nice if some of the crimes were stopped before they happened right? It doesn't have to be a full on Minority Report style world but proactive measures are necessary to stop crime before it happens.

The other approach would be confirming the involvement of known offenders. They arrested a number of people. If they can tie those specific people to known usage of a site, say by linking their IP address to a known location or a known email address, then that would further build a case against them.

[1]: NOTE: I'm purposely ignore medical and legal related content here as they'd be covered by separate confidentiality provisions.