Basil,
1) Why bring this to the top? Are you stating the King Power scams are starting up again? Nothing has been reported locally for months maybe even years.
2) Just where are these tales of violent taxi drivers? Considering the size of this city and the amount of taxis, incidents with foreigners are few and far between. Dishonest? Not really. The odd one tries on the "meter not working" scam. If it's not reading 35 Baht when you get in, just get out again and jump in another one, there are so many available that you won't have to wait too long.
This is still one of the most cost effective, taxi friendly cities around .