Balassone says he thinks the amount of cash changing hands also matters.

"If it was a couple of dollars, it’s an acknowledgment that you exist and you help me earn my money and I appreciate it," he says. "If you told me it was $20, given the amount of money involved, that sounds like it’s a pay-to-play."

That's the ethicist's view. How do things look from inside the industry?

"It's a combination," says Emil Lawrence, a veteran driver who once had a newspaper column called "The Night Cabbie."

"If you feel that you’re not going to get any business from the cab company unless you have to pay them, it’s a bribe," he says. "If you feel that, hey you’re getting business already and you’re tipping them for extra business, then it’s a tip. The problem is in the majority of cases you don’t get anything unless you give them money. I’ve worked for eight or nine cab companies, and every cab company has their own unique situation, but every one of them, I never got my taxi unless I paid an implied tip, which was actually a bribe."

One driver who said he wanted to remain anonymous because he is afraid of repercussions at work, sums up the fine line on this issue: He says he tips the guys in charge of the cabs "essentially so they'll like me. In principle, it's similar to tipping a waiter/waitress for good service, but the consequences for not tipping may be greater. If I am sick one day and have to ask if they can find another driver to cover my shift, they'll be more likely to do it because they know I'm a regular tipper.

"Yes, I'd prefer not to tip," he says. "But the dispatchers don't earn much salary so they deserve tips. But at the same time, they also have enormous power over cab drivers since the cab companies give them the power to issue the cabs. It should be plain to see then where the abuse can occur. Cab companies will show good PR manners about this in any interview with the press. They've downplayed it before by saying tipping is simply etiquette and cab culture. But I honestly don't think they really care as long as drivers pay their gates."

The tip versus bribe discussion glosses over one central point: Whatever you call these payments, they're illegal under a city ordinance, and cab companies are liable for violations. But officials at the San Francisco Municipal Transportation Agency responsible for enforcing the law say they can't prosecute anyone without driver complaints. And drivers, in turn, are reluctant to blow the whistle on the companies because it could threaten their livelihood.

Balassone says whether the gratuities are tips or bribes, the real question is what's going to be done about the practice. "If you rationalize it, it doesn’t go away, it doesn’t reach a level of import so that someone thinks they have to do something," he says.

"This is wrong from an ethical standpoint. One of my thoughts is, 'Enforce the law.' Either get rid of the law or enforce it. You have laws and don’t enforce [them], then people get cynical. I would figure out a way that the cab company would have a huge fine if there was money being taken from the cab drivers. You fine two people 10 grand, you will fix the problem. There has to be a will to do that, follow-up, and some courage."

Jim BalassoneJim Balassone

The Fine Line Between a Tip and a Bribe for Those Who Drive S.F. Taxis