denial of service attacks seems to be related to the Russia-Georgia conflict. one user was the key target for the dos attempts against facebook, google apps and twitter, and twitter seems to have been the worst hit.
http://feedproxy.google.com/~r/TheNextWeb/~3/N5hLSzygaz0/
http://www.nytimes.com/2009/08/08/technology/internet/08twitter.html?_r=1