If you shoplift from a store wearing a fake mustache, and saying your name is "Mickey Mouse", you aren't committing fraud, just shoplifting. If you download documents with an anonymous name ("Gary Host", not the name of a MIT student / staff member) and an anonymous MAC address (once again - not passing yourself off as anything other than a guest) you are guilty of copyright infringement, not wire fraud. Using a script to rapidly change your name / MAC address might be a different matter, as you are pretending to be a crowd of people (and it's hard to respond to). But there's nothing he did to circumvent the security that was intended to make a material misrepresentation, he simply did the equivalent of using his hotmail account to create a new account once his gmail was banned.

For things like fraud, there's no hard and fast laws. The courts use a thing called "common sense" (or precedent, which is using a previous judge's common sense). The bar for fraud is pretty high - he had to have misled the victim, and that misrepresentation must have made them behave differently (among other requirements). Had he used his own name, and used a new laptop instead of spoofing his MAC address, he would still have been able to download the documents.

But that's just my opinion, and IANAL.