These little "groups" of children are everyone, you can no more be ware of them than you can change the whether.
The unfortunate, and frankly saddening thing is, most of them have enough talent to succeed in taking most sites down. Begs the question as to why they don't do something worth while.
p.s. This is just my little annoyance, but try not to dignify them with the word "hacker". "Hacking" entails a target for a specific reason, whereas these people will take down any site just for the fun of it. Script Kiddies.
Matt