Mears operates several cab companies -- Yellow Cab, Checker Cab, City Cab, and Safety Cab. Each has its own designated pickup zone.
Yellow Cab, which ironically is orange, is authorized to pick up at the airport.
Checker Cab, which is ironically yellow, is authorized to pick up at Walt Disney World. They are the only cab company that can solicit business at WDW. There are gypsy cab companies out there (Check-Her Cab, Check-It Cab, Chek-A Cab, etc) that will try and solicit around property. They can only pick up if they either have a pre-assigned reservation, or if there are no Mears cabs around.
Now, I'm not saying one is any less honest than another... they are ALL independant contractors, but with Mears, you do have recourse in the event there is a problem.
Also, with Mears, drivers are required to show and validate thier drivers license before they can get a vehicle. My best friend used to work a security kiosk at OKW, CBR, and WL, and I can't tell you how many other cab drivers did not possess a drivers license. So who knows if they even had insurance, etc.
I'm sure there are plenty of other cabs out there that are legit, and honest, and are great companies... so it's sad that a select few give the rest a bad name.