One thing I've learned over the years is that you can't take it as gospel when a customer says "I want X". When following a customer request to the letter, most times you'll end up regretting the decision.
For us, the better way to handle when the customer asks for X, is to sit down and create a persona and ask ourselves why they are asking for it, and who else would want it.
I find we get a much better result when building requirements based off the customer's pain rather than just giving them what they want. It helps maintain usability by avoiding confusion over additional features and functions.
Then again, in a startup environment this is a tricky balancing act. You can't forsake sales for a drawn out product management/development process, but you also can't just add every customer feature request either.