The men and women who sell advertising are among the nicest people you will ever meet. In the interest of full disclosure, I’ll also tell you that I’m a salesman’s kid, so I have a soft spot for good salespeople. Many of them have a genuine interest in you and your company’s success, and want to do everything within their power to help you make that happen. But if you’re going to regard salespeople as trusted advisors, please don’t lose sight of who employs them and how they are compensated.

There’s nothing wrong with asking for advice, or even accepting it when it’s handed to you without a request. But before you base your decision on the advice, stop to ask yourself whether the person who provided it has a stake in what you’ll do.

If they’re selling on any kind of a commission, their compensation depends directly on what they get you to buy. The more you buy, the more they make. When they suggest that special, limited-time program, they may be receiving a special incentive for it.

If you ask a sales rep from the local newspaper how you should spend your ad budget, you will probably get a strong urging for newspaper advertising, along with research supporting that recommendation. I doubt that you’ll hear, “I wouldn’t choose newspaper now. I saw a study saying that radio works well for this kind of product.” It’s not a matter of deceit; it simply means they are loyal to their employer, the medium they know best, and their own self-interest.

That’s okay, as long as you don’t lose sight of your own self-interest, because the salespeople aren’t going to focus on that. No matter how nice your rep may be, and no matter how much interest she appears to show in your bottom line, never forget that she receives money by taking part of yours. That doesn’t mean you shouldn’t ask for or listen to her advice — you just can’t afford to forget that she’s a salesperson, not a disinterested advisor.