It just means that somebody that had your email address in their address book got infected. The people it is being sent to is some of the other names in their (the infected person's) address book. So far this time it has been mostly just a waste of time and fairly harmless. Still it is of some concern that people (like me) that have never seen hide nor hair of a virus had it showing up in their email multiple times. I must have got 25 of them before Earthlink started screening them out. As long as you just deleted it, it was harmless.
The speed at which it spread though was astounding. This was version F of Sobig, and it is getting better with each version. In a few more versions is it going to turn into a major problem? Might there be economic ramifications? The news accounts seem to indicate that yesterday there was a race to get certain computers disconnected from the net in time. It's certainly something to keep an eye on.