This whole thing is a can of worms and it may not be sorted out clearly and legally for decades, however, copyright (in the US anyway) means the rights to all copies, which includes digital. So if a site's terms of service and copyright notice says you can't save a copy of the site for personal use, then you can't do it legally.
Not really true. Unless you explicitly agree to a TOS or EULA, (thus entering into a contract for the use of the material) a TOS cannot overturn fair use. Single copies made by individuals, for individual use, are well within fair use.
The ruling regarding robots.txt is a bad ruling made by a judge who is trying to make the the best decision for the one instance before the court, not establish good law for all cases.