Earlier quoted context omitted.
I didn't read the parent as paranoid at all. I thought it was pretty cool. Further, wrt the optimal/most direct route thing: * the algorithm could be tweaked to "adpresence" en-route fairly easily * "most direct route" is an ambiguous term. There could be two routes that involve almost same distance in miles, but the slightly longer one is likely to take less time. Which constitutes most direct? It turns into an opti…
There's a crucial difference between what you're proposing and what the parent suggests - user choice. At least as I read the parent, he's not saying you're given a choice of what route, etc. That seems like a crucial distinction to leave out if he meant that it would be at the request of the user.
If you get in a cab and say "take me to $x" it is the cab driver's responsibility to take the best route. However, since metering is distance AND time based, there is a lot of wiggle room in what best route means. It is always an optimisation problem, and relies on imperfect data of the future conditions of the route. Further, in most american cities, there are many routes that are no more or less direct, as a result of the grid system. Therefore the car taking you on the route that goes past paid displays is not kidnapping. It is choosing 1 of n equivalent routes - the one most profitable for the operator, while still meeting the criteria of the user.
Further, even with advanced traffic and condition understanding available to a robotic car, the ability to choose optimal path will probably improve significantly, even when the small fudge factor to go past advertising is accounted for. So what if it is 30s less optimal on your ride to go past the advertised place, when the human cabbie would have chosen a route adding 5 minutes?