My business was a one vehicle business, picking up folks at the airport via internet email requests. I had a website offering these pickups.
Once the taxi folks started noticing my van driving in a couple of times a week, the "I'm just picking up friends" excuse didn't cut the mustard with them any more.
My driver started parking in the parking lot, walking in and holding a sign for the person, and subsequently walking back to the vehicle to leave. That got the "Why do you have to hold a sign to pick up your friends" routine.
After a few more times of this behavior, the drivers got increasingly menacing towards the driver, including stopping him in the parking lot and pulling him out of the vehicle and pushing him around, before finally warning him the next time, it would be worse.
That's when we pulled the plug on SDQ deliveries.
We continued on with POP deliveries that were less frequent(once every 7-10 days) and encountered the same attitudes and treatment within a couple months time.
That's when I gave up.
To clarify a little, this all transpired back in 2002, but I have no reason to believe they've become any friendlier to folks encroaching on their "right" to move all tourist traffic.
I wish Thomas all the best.