The trouble of all this stuff is that for 'generic' use you don't need technologies like this at all. There is nothing new required to firuge out how many active cellphones you have on a certain road, how fast thay are travelling, etc. The point here is that they are linking actual _persons_ to these little spots on the screen. And that's why privacy is a concern. A cellphone as such is a number, but now you're adding a face to it (with locations, behaviour tracking good for data mining, etc). You even have ad 'conversions' as you can tell if a person actually went to a restaurant you suggested. Also, never forget about phishing practices, these will not disappear but likely adapt to the new medium as well. A privacy-wise well educated person can understand the benefits and risks and make his/her decision, but plenty of people can't or won't really understand what they're getting into. Many social sites have the same problem, but those are much more virtual and hence pose less risk.