Friends in the hobby who know I am an attorney ask me what I think of the Black Book.  I've read a lot of what's been written here, and maybe I should have read it first before answering questions.  But this is my take on it, looking for yours:
1.  Nobody knows what LE is going to do with thousands of names.  My guess is, not much.  The return on investment isn't that great.  But who knows.
2.  The possibility of this document never seeing the light of day seems slim.   It would not surprise me if someone got a hold of it, say EndDemand or some other such group, and posted it on a web site.
3.  Having said that -- what's the signficance?  Assuming LE is not going to use the information (and hopefully not), who is going looking for your name in the vast landscape of the internet?  If  your SO is looking, she is already on your track, I guess.  And you'd have to have a pretty unusual name for it to stand out anyway.
Just my thoughts.

Does your career lend itself to googling? Will someone make a creative google map of these folks? How unique is your name? Will anyone care in the age of wikileaks? Would anyone at your work wan to start a rumor?

Traditionally, one has needed to catch a person in the act for an offense, but the Internet has changed all that. A name is not enough.  E-mail, posts, name, phone calls and traceable deposits are closer. In the end with so many tight budgets, this comes down to money and the costs to pursue. We know who had the money in this case.

We are in the age of Persistent "traceable" Identity.  Best to join the ranks of the Anonymous.

Indeed, and I know at least one person who never let out his name . . . .
Yes, the subject is more harm to reputation that prosecution.  I know I'm not important enough for the LE effort.  Even googling a common name can lead to uncomfortable questions.  Short of anonymity, deniability is your best friend.

Just curious why you think there's little chance the list won't see the light of day? You said you've followed all the case news, so I'm assuming you've seen that both the prosecutor and defense attorney filed a joint motion (which the judge granted) to shield the list from the public.  The judge wouldn't even let the defense attorney get a copy of the disk/list so how is it going to get out? Short of someone at the US Attorney's office going against the Judge's order and making copies and turning over to the press, this seems unlikely.  If they do it would be cause for defamation and libel lawsuits galore.  Attorneys I've talked to up in Michigan where I went to school think there's little to no chance it gets out.  This is because of the high profile politicians/businessmen on that list that used MC's services (and some who likely didn't but were added to it by the defendants in case they were busted).  I wouldn't be worried about this at all.  Also, the likelihood of LE trying to track down and prosecute 30,000 customers seems remote.  Simply being listed on a client list is not enough to prove guilt in a court of law.

Ah just kidding

Completely agree on (1) prosecution unlikely or impossible just for being on a list and (2) no official releae of the list.  The concerns I have heard (I was not an MC customer) are more related to exposure that SOs, bosses, etc. might pick up.  

The question is more practical than legal.  "See the light of day" was my phrase.  I do not think something of this level of interest can be hiddden, my .02.  Unless only one copy exists, which seems unlikely.  Could be no one will try hard enough.  I'm just a cynic at heart, though.  Seems like anybody can get anything.

Minor correction:  the penalty for the US Attorney releasing the list would be contempt and/or disbarrment.  Don't see civil liability absent a statment like, "everyone on this list is a John."