Just playing a devil's advocate here. The way archivists are downloading the data can be said to disrupt the services, which is mentioned in the terms of service:

2. d. viii: "interfere with or disrupt the Services or servers, systems or networks connected to the Services in any way."

I'd also like to point out that the apparent spokesperson Brenda Fowler said in her open letter to Verizon, that "If the problem is that all our attempts to rescue our archives in the time we have left is causing an overload or strain on your servers, then stop making us HAVE to work around the clock, and GIVE US MORE TIME. ..." Probably not the wisest thing to say right now.

Also, archiving the groups with automated tools is against the Use of Services rule, that states the following:

2. e: "Use of Services. You must follow any guidelines or policies associated with the Services. You must not misuse or interfere with the Services or try to access them using a method other than the interface and the instructions that we provide. ..."

As I mentioned in another comment, I really support the cause and am a big fan of archiving myself but it's unfortunately quite clear that Verizon is right at calling out the violations of "terms of service".