I don't begrudge them this income stream from people who buy domains but don't do anything with them for awhile. What's the harm?
There are 2 main issues I have with this:
1. It's not "unused domains" that get this treatment. It's any domain that uses their DNS. I had several active sites and was shocked to find that blahblahblah.mydomain.com pointed to one of their spam pages.
2. If you went to spammysubdomain.realcompany.com and found a spam page, who would you think was responsible for it, realcompany.com or realcompany.com's registrar? I'm guessing almost everyone would think that the company themselves did it. By name.com doing this for active domains, they risk damaging the domain holder's reputation, for anyone who happens to stumble on to one of the spammy subdomains.
Typo-squatting is addressed by both the ACPA (http://en.wikipedia.org/wiki/Anticybersquatting_Consumer_Pro...) and the UDRP (http://en.wikipedia.org/wiki/Uniform_Domain-Name_Dispute-Res...).
And worse, you're held responsible for the content of that page.
I feel like you're not. When the subpoena is served, it will be to the owner of the IP with the content on it, not the owner of a random DNS entry that happens to resolve to that IP. Even if it does, I imagine the exchange going like this: "Your honor, I have no access to that server and can't control the content in any way." "Right, this is a waste of my time."
Contracts can say whatever they want. Whether or not they are actually enforceable is a whole 'nother ball game.