Replacing the Comcast webpage with a shout out to other hackers was a stupid, immature prank that could be performed with a relatively small amount of technical skill in a relatively short period of time.

Stupid pranks that have a significant negative impact on people's lives should have serious consequences associated with them.

However, immature pranks have an entirely different character than actions taken through malice or greed, and Justice requires that we recognize the difference between those categories of behavior. Furthermore, computers, internet connections and websites go down, on their own, all the time. A 90 minute outage for Comcast's website is not something either they or their customers should ever have to endure as a consequence of someone else's irresponsible behavior, but it is something that they and their customers do, in fact, endure on a regular basis. All the time.

Given these facts, a year and half in prison is way outside the scope of what justice requires in this case. Its a sentence that is so far outside the scope of what is objectively reasonable that it shocks the conscience. It seems an obvious consequence of technical ignorance on the part of the decision makers as to the actual mechanism through which this outage was created and to its actual impact on users of the network. This sentence is a far greater evil than the act it seeks to rectify and it should not pass without remark.

Comcast.net Hijackers Sentenced to 18 Months | Threat Level | Wired.com