There are many obvious case where this is not true: for example in the case of breakthrough /emerging technologies. Customers are generally pretty good at telling you about things they'd like changed about a product of yours they're using. But ask them if they're interested in a product of yours that they may not be very familiar with, with benefits they may not completely understand, and their answers are notoriously unreliable!
Why do I bring this up? I signed up for DVR a couple of months ago. I also signed up for the HBO package for the very first time (more on HBO's really smart On Demand options later.)
I didn't really expect DVR to significantly change the way I watch TV, but it has. Completely.
I've basically stopped watching live TV; even when I show up in time to watch the shows. People who own the TiVo tell me the same story. Once you get it, you can't do without it. However, getting people to buy it in the first place has always proved to be ridiculously challenging.
The standard ways to acquire new customers (promotions, introductory offers, the right kind of marketing communication) just don't seem to do as well in these situations, especially when there are already existing substitutes for your product. Thats where creativity is required to convince customers of the benefits of your product over whatever they are substituting it with.
Revisiting TiVo, I appreciate their product and their marketing challenge even more now.... Their "my TiVo understands me" campaign doesn't really work for me though.:)