Only if the person on the receiving end says "You gave that to me for free once, therefore I will never pay for it again, and if you refuse to give it to me for free henceforth I will never do business with you again." That is incredibly selfish and ungracious, and, unfortunately, is an attitude held by too many in this world.

On the other hand, if that person appreciates it for what it is--an unexpected and undeserved gift--both the giver and receiver are rewarded. And perhaps others too, as more "gifts" are given down the line.

One specific business example: A relative of mine liked a certain brand of peppers, and was fairly loyal to that brand. On one occasion, a jar of peppers was of lower quality than usual. My relative wrote a nice letter to the company, telling them how much she liked their product but that this particular jar didn't meet the company's usual high standard. Much to her surprise, she received not just a letter in response, not just a coupon for a free jar, but an entire case containing an assortment of the company's products. Since then, I don't think she has bought peppers from anyone else.

Finally, to bring this back to UA, my personal experience. We used to fly whoever had the cheapest fare. One time, that happened to be United. For whatever reason, the agent gave us no-status fliers Economy Plus seats. The difference was so noticeable--particularly when compared to another airline's 737 seats that we had recently flown in--that I resolved to at least get Premier status so that we could reserve E+ every time. For that, and other reasons, United continues to earn my business.