Again, this is all speculation and hypotheticals since I don't have enough information on the specifics of the Childs case to come to any meaningful conclusion. I would love to have more information on this case, however. If anyone has anything more detailed than what's been released to the press, I'd love to hear it.
Given the facts known, Childs certainly did something he shouldn't have, but unless he dropped a logic bomb in the network, it's barely a bump in the road.
If you really wanted to make a point and mess up the network, there are many better ways to do it. You could place a box near the core somewhere that randomly swaps bits in the datastream. That would certainly cause problems, but would also be discovered quickly.
Better yet, write a few database queries that randomly swap numbers and letters in various database fields. If that script started out slow and then grew in scope over days and weeks, it's likely that by the time the problem was discovered, most of the backups would already be tainted, and anything using that database would be basically unusable. For a municipal government, the data loss and time required to fix that problem would be significant, to be sure. Most or all criminal and tax records would be compromised and chaos would ensue. Interestingly, I wrote about this very scenario several years ago. The cost to fix problems like that would carry a heavy pricetag, indeed. Maybe even millions of dollars.
Don't get me wrong -- I'm not defending Childs' actions in any way, shape, or form, I'm just pointing out that there's a world of difference between letting the air out of a car's tires and wiring a bomb to the ignition switch.