Meet the latest celebrity virus (well, worm) - Klez. Wired's article mentions a really nasty feature of this one whereby the
From: field uses one of the email addresses it's collected to send it on to the next person. So, the confusion and hassle it causes is that much worse.
This is a major problem for people who barely understand how the system works in the first place; plenty of people assume the
From: field is always true. On top of that, mailling lists which automatically subscribe people without sending a confirmation email are signing people up based on this virus's activity. So there you go, the geeks were right on this one. Making things user-friendly needs to be done within limits, for good reason.