http://www.cgisecurity.com/articles/anatomy-of-web-app-worms.txt

Impact of the worm:

Obvious impact would be halt of commercial services, bandwidth charges, system performance,
time to patch (Time = Money), upgrades, cost of creation of patches, and various other nasties.
Of course security companies would profit from such a incident , and who knows, perhaps some of
these worms are created by security companies to increase production/sales.