They suspect that the worm opens a gateway, which will allow your computer to be turned into a zombie and be used to send more spam e-mails.
Here is a portion of the alert from Sophos:
Experts at SophosLabs™, Sophos's global network of virus, spyware and spam analysis centers, have warned of a widespread worm posing as a St Valentine's Day greeting which is spreading fast across the internetSophos alert, here.
The W32/Dref-AB worm has been deliberately spread via email in readiness for office workers and home computer users to find the malicious Valentine email in their inbox first thing in the morning. Since midnight GMT the Dref-AB worm has accounted for 76.4% of all malware sighted at Sophos's global network of virus monitoring stations.
Subject lines used in the attack are many and varied, but all pose as a romantic message. Some of them include "A Valentine Love Song", "Be My Valentine", "Fly Away Valentine", "For My Valentine", "Happy Valentine's Day", "My Lucky Valentine", "My Valentine", "My Valentine Heart", "My Valentine Sunshine", "Send Love On Valentines", "The Valentine Love Bug", "The Valentines Angel", "Valentine's Love", "Valentine's Night", "Valentine Letter", "Valentine Love Song", "Valentine Sweetie", "Valentines Day Dance", "Valentines Day is here again", and "Your Love on Valentine's".
Spam is getting out of control and seems to be defeating spam filters (too often). Here is more evidence of this problem:
2006 was the Year of Internet Crime - 2007 is predicted to be even worse