In this article which talks about an attack on the root servers that support the Internet:
The engineers are "scratching their heads" wondering why the attack was performed.
I can think of a few reasons.
1. Reverse load testing. Hackers are trying to calculate what it will take to bring down the Internet. Bringing down the Internet could cause a myriad of disruptions that might be beneficial to a myriad of sneaky, slimy people.
2. Bringing down the Internet at a particular time when a certain crime is being committed may prevent certain communications which may then alert the authorities or warning systems to the crime underway.
3. Someone wants attention.
4. Some really flawed programming.