The old debate in market research between quantitative vs qualitative is very much alive. With the introduction of cheaper online quantitative methods*, the easy reach of social media, and data minning, marketers seem to have found a cost effective alternative to traditional market research. However, the question persists: Are online quantitative methods a replacement for other methods of Market Research? I would argue that one answer lays on the setting of the firm.
In industrial settings (B2B), quantitative approaches may not be that useful. This is because B2B environments tend to have a small number of players in a business category. There, personal relationships are more valuable. When the number of important actors is relatively small, deep interviews to opinion leaders, and industry experts would be more important. On the other hand, in a small business, an entrepreneurial initiative, or a firm with a strong online component in its business strategy, then social media might be more relevant, simply because it is way cheaper, and fits the business model.
Last, if we speak about a large B2C corporation with global presence, then it is quite likely that a specialized supplier would be in order to handle the scope. Even then, I would not settle necessarily for polls or surveys, but ethnographic observations, mistery shoppers, or any other method from the applied social sciences, which often are neglected. Armchair researchers, might not arrive to relevant insights simply because they are not where action happens. One can learn much more of just being at the site, seeing people, and interacting with them. Get a customer-service uniform and spend a week at one of your stores. Nothing can beat that.
* like http://www.surveymonkley.com