Backhanders is a very negative term. I have never done it.
HOWEVER, I have in the past luncheoned with prospective clients in good quality restaurants with fine wines etc, and this has to have swung the deal in my favour. In certain industries, it is what is EXPECTED. Deals will be done this day in restaurants, hotels, on golf courses etc. Networking with incentives is a great way of getting work. Is that not why we all have a business card and a T & E column in our books?
The end result that you get the work, is the same. But how you view and go about it can either be done in a slimy, underhanded way or in an open and very professional way.