The New York Times article here reckons that Minority Report type tech will be on our high streets very soon. Which will be cool, I guess, as long as a) it works and b) it doesn't just become another way to spam people i.e personalised spam.
I would definitely like it if a billboard recognised my face, looked at my hobbies & interests in my profile, then pinged me with a nearby sale on the stuff I liked. I can see how this would be extremely powerful for brands - a combination of personalisation, location and impulse buying. Plus, it would be extremely measurable.
Or, could it freak people out massively as an invasion of privacy? Probably, but if it's made to be opt in through Facebook Connect or Google's Direct Connect, then many of the privacy objections will be overcome. Making the system opt-in would hopefully stop spamming - people would soon opt out if they got pinged with loads of crap.
I guess we'll find out soon enough. With any new technology, one brand will do it really well and set the standard for best practice and another will do it really badly - both of which we'll learn from.