I can certainly understand your frustration with the situation, and your subsequent posts here about the difficulty your friends have experienced make it clear why you are concerned. What makes these things so hard to deal with are the nuances of law when it comes to the various statutes, in various jurisdictions, regarding "hate speech", "terrorist threats", and the other terms used in the plethora of laws rather recently, and sometimes hastily, implemented to deal with such things (which I'm sure you understand!) .
For instance, I know from experience that the situation you describe where "I have friends whose home addresses and phone numbers are being posted along with "I hope you get yours" type notes." will not result in a criminal filing in most California jurisdictions (lacking a direct threat, solicitation, or conspiracy component). So, absent a judge determining otherwise, whether or not is it "illegal" is not as clear as one might initially think, as distasteful and potentially damaging as it might be.
I suspect that, as an attorney, you understand the difficulty this presents for a hosting provider that has the responsibility of operating within the law and has chosen not to censor the speech of their customers according to their own, or another's, sensibilities. Many hosts do undertake such control of content, but DreamHost does not. They do, however, comply with the law. The end result of this posture is that, from what I have seen over the years here, they will not make the determination of "legality" except in the most clear and unambiguous cases.
I believe they will investigate your complaint (I know for a fact that they have staff that is dedicated to handling these issues specifically), but I suspect this may not be as "clearly illegal" a situation in their views as it might first appear to you, or another (but that is just my opinion, and it's worth precisely what you paid for it).
Interestingly, like another poster here, I visited the site, and did 20 "random" page displays without seeing any personal information or threats that even remotely approached what the California authorities I have dealt with in the past would consider criminal (though I did see several references to such postings).
Hopefully, the authorities will give your complaint proper attention. One thing I suggest is that you may well have better luck with a local or state law enforcement agency if you are in California - California laws are a bit more "strident" than the federal law in interpreting such things, and the ic3 may not give your complaint as serious a consideration as a state attorney general, district attorney, or sheriffs office or police department that would ultimately have to deal with any violence resulting from such conduct. Just a thought.