"They could have been saying, 'Look what I can do to Twitter. I think my botnet can handle whatever you want it to do,'" said Abrams. "I'd put my money on this being a demonstration, a show of force, by someone looking to hire out their botnet."

Graham Cluley, senior technology consultant for Sophos, told Computerworld that whoever launched the attacks should beware the clout of those he's going after.

"Anything is possible, and we could make guesses like this until the cows come home ... We simply don't have enough information yet to be certain as to what the motivation was," he said. "One thing is certain -- if they did do this as a demonstration of how powerful their botnet is, they've just made themselves some new and angry enemies in the shape of some major Web 2.0 companies. I wouldn't be surprised if the computer crime authorities put some serious effort into trying to track down whoever was responsible. After all, if they can bring down social networking sites they can bring down banking sites."

Cluley also said it's not yet clear why Facebook faired so much better than Twitter. It could have been that the bulk of the assault was aimed at Twitter or that their defenses simply weren't as tough.

The attack against Twitter brought the site down between 9 a.m. and 11 a.m. EDT this morning. This afternoon, the microblogging site was still struggling with slowdowns and interruptions caused by the assault.