I found that MetroCab in Santa Monica takes credit card, and there was no additional fee for me, over what I would have paid for with cash. There was no complaint and cabbie was generally nice about it.
The other cab, on the way back from LAX though, said he could, but that his machine was broken, too much trouble, and complained a lot like a lazy bum, so I just begrudgingly gave him cash. Then, he wouldn't give me a receipt so I could get reimbursed by my company! grrr..
