Where do you draw the line between a business offering an incentive for you to fill out a survey and an attempt to buy your opinion outright? And just what would a business need to offer you for you to part with whatever principles you might have?

Consumerist reader Liz writes in about the service center at her local car dealership in Maryland, where she was tempted by an offer to buy her opinion.

“The service was fine and I have no complaints,” she tells Consumerist, “but as I was checking out, I was told in no uncertain terms that if I gave a perfect rating on the survey that I’d be receiving online and by phone that I would get a free oil change. So I guess they think I can be bought for the price of an oil change.”

Liz tells us she has no intention of taking them up on the free oil change, but we wanted to know just how easily your opinion can be swayed by the prospect of a free oil change:

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