In 2012, Facebook won a judgment in a case against Power Ventures in a case where the defendant had provided a work-around to Facebook users where specific IP addresses could be banned from seeing certain pages. The case is described here. To win the case, Facebook had used various federal anti-hacking statutes that provide criminal penalties.
Electronic Frontier Foundation has a story Dec, 7 about an appeal before the Ninth Circuit of the case, here. EFF argues that it should not be a crime to get around an IP block. The reasoning is similar to another case where EFF argues that it should not be a crime to violate an employer’s computer use policy (which could have the potential to spill over into personal areas, covered here Dec. 3).
An IP Block is significant in other areas. It can be done (with server-side scripting that some web-hosting companies will provide) as a defense (most commonly) to DDOS attacks, even by a public website, or possibly to hinder a perceived stalking threat. If a particular person found his home IP addressed blocked at a particular site, could it be a crime to access it at a local Fedex-Kinko's or even from a hotel? That sounds rather much.