Well, that's an interesting comment because last time I was in London I noticed they've really jacked up the cash price of single tickets on the tube, to the po

Well, that's an interesting comment because last time I was in London I noticed they've really jacked up the cash price of single tickets on the tube, to the point where you'd be an idiot not to get an Oyster card because using one makes multiple trips much cheaper. Differential pricing like this could be used to effectively buy people's location information.