I personally believe that assumptions are the mother of all screw-ups when it comes to relationships in general, and business relationships in particular.
When we make assumptions, we're limiting ourselves to a narrow view of things--a tiny window from which we view the world. Nine times out of ten, our perception of the world doesn't match anyone else's, yet we base many of our day-to-day decisions on assumptions born of our personal viewpoint of the world, instead of that of those we are looking to influence.
You've probably seen evidence of this in your own life, and with your own business. You might assume your child wouldn't like a particular dish even though they've never tried it, so you never offered it to them. You might also assume your customers wouldn't go for a new product, so you didn't test it in the marketplace. But you didn't have proof that either of these was true--you made assumptions based on how you view things. How many relationships (both business and personal) have floundered because decisions were made from a narrow point of view (our own)?
We all do it--but it's absolutely the wrong attitude to take--especially in marketing. Why? Because we are NOT our own customers! I see it time and time again. "Oh, they'll never buy that... That person isn't interested in my business... They'll think my idea's stupid..." Really? How do you know for sure? We cannot assume that others feel the same way about things as we do. They probably don't!
We learn this in Marketing 101 (know your customers), but we quickly forget about it. It's so much easier to fall back on our own thoughts and feelings. However, if you've ever taken a course in the Psychology of Sales, you learn how important it is NOT to make assumptions. Successful sales people learn to read their prospect's "map of the world" before discussing product or service with them.
If you want to be successful, then always be challenging your assumptions--break out of the narrow view and be willing to look at things through a different lens. That's what innovators do. Companies like Apple and Netflix, for example, took ideas that some might have thought were stupid at the time and stepped out of the mainstream. Their leaders took a chance and acted on an idea, and that idea developed wings and took off because they understood their customers' map of the world. They made it their business to find out what problems, wants, needs and desires their customers have--and developed something that filled those needs.
In other words, they got themselves out of the picture and concentrated on looking at things from their customers' point of view
One of my favorite humorous examples of the problems people have with assumptions is from an old TV episode of "The Odd Couple." Tony Randall, who played Felix Unger in the series demonstrates it on a chalkboard perfectly in this video clip (A MUST WATCH), Never Assume because... .
All humor aside, however, I think it goes beyond just avoiding the problems that follow when we make assumptions. When we make a conscious effort to get out of our own way and look at things from another person's perspective, good things happen. Relationships grow, ideas flow, and we make better decisions.