Marketing research is extremely important. Companies that are really marketing oriented recognize that they need to always be in touch with what's happening in the market (and so should you). Customer needs are constantly changing, often in ways that are very subtle. If we consider the history of computing, where we went from huge machines, to smaller ones, reaching the home personal computer; and from disconnect machines to the need to connect them as a network and then to the Internet. There were then so many resources online that there was a need to sort them(as Yahoo did), and them to search through them (as Google did). More recently, there were a need to take the physical life social experience online (as Facebook did) and now we can feel that the people need is to take the internet everywhere they go, and we are slowly going mobile.

Many technological revolutions happen accidentally but most of them are the results of relevant research and observation. On the Internet, there are many (cheap) ways a programmer can find out what people want: 

Internet surveys: usually managed by email or by a specialised web service like Survey Monkey.
Website traffic analysis: Measurements of the areas of the site most frequently visited, which products are purchased and the payment method used.
Marketing databases: Inviting users to create accounts on your service, deriving profiles by gathering relevant information about those users. Therefore knowing your users and their needs better.
Prototype testing: simply to make some users test the basic version of the application before it is completed, to see if they get the idea and if they like it, what they like about it, what they don't.

Next : Marketing segmentation and targeting