the concern is how privacy of those who opt in will be maintained in the long term. Also, if it makes you (and society) safer, how much safer? Is it worth giving up any privacy?
It's fairly analagous to privacy concessions made through the Patriot Act.
the data already exist, right? (i realize they talked about creating a new type of crippled data basically for the sole purpose of not using the existing data), you're just opting in to letting it be used for virus fighting.
your permission only extends to that. giving permission for that doesn't imply that you agree to the govt doing whatever they want with the data. i don't see any slippery slope crap. if they don't care about your permission, they could just take the data now.
i mean, i think it's paranoid and weird to care at all. but if you do care, the opting in to do your rough ridin' part to prevent an economically crippling virus from killing millions of people doesn't change anything.