Intuit, you'll recall, has since backed off of using product activation in future releases, after a huge backlash from customers (and likely a resultant surge in TaxCut sales). Symantec has already done product activation trials, activating 250,000 customers with "negligible complaints" according to the article, so perhaps they'll fare better than Intuit. Of course, if consumers just decide they don't want product activation, there are any number of other AV software companies who will take their money.
Personally, I'm somewhat surprised that Symantec hasn't simply tied automatic virus definition updates to a valid serial number. I would think that would take care of the problem for the most part, without the stigma of product activation. If a particular serial number pops up several hundred times, assume it's attached to pirated or counterfeit product and disable it.
The kicker, of course, is that this is Symantec we're talking about. If their product activation routine is as slow and bloated as the rest of their stuff, it'll suck up 128MB and 40% CPU time, and take 20 minutes to activate over a broadband connection.