If your computer starts insulting you, you might be infected with Cisum.A:

A new worm, Cisum.A, is spreading through network connections, throwing insults as it goes. Once a computer is infected a message is displayed in a new window stating, "YOU ARE AN IDIOT!!!" Additionally, an MP3 file plays a message with the same phrase and repeats it every 5 seconds. The malware also disables any anti-virus and firewall software that is on the PC. In a strange twist, Cisum.A also looks for Bagle or Netsky infections and attempts to remove them. The virus is currently rated as a low threat by Panda Software.

The most interesting aspect of this particular worm is not the insults but that it identifies and remove other virus infections. Is this the start of a new phase in virus development? Viral warfare, where virus authors fight for market share by infecting unsuspecting users (idiots) with antidotes for their competitor's offspring.