Do you remember Conflicker? The virus that in December has started to spread automatically exploiting a Windows Bug.
According to experts, that virus is designed to activate itself on today, 1st april 2009!
What will happen?
- Data loss?
- Massive spam sending?
- Massive distributed attack to other computers?
- Sending of sensible data to evil servers? (like: password, credit card numbers)
- April's Fool
In my opinion is the option #2... but i hope in an April's Fool! 
Update: how to detect if your computer has been infected