Does the Question of Addressable Market Matter?

I read an interesting post on Ask the VC about how the concept of an addressable market is evaluated, when the product or service is trying to solve an emerging problem and opportunity that is about to hit in the near future. The example given in the post had to do with Feedburner’s ability to raise money before bloggers realized they needed feed management and before VCs realized that they could monetize this model: Capital was raised based on the belief that the market was going to emerge and the product was going to be there as a solution to address this new market.

According to VC Brad Feld, there are two schools of thought that govern this area: One camp believes that evaluating the TAM or total addressable market does matter, while the other does not.  Feld is in the DOES NOT MATTER camp:

I’m in the “measuring TAM doesn’t matter at all” camp, especially in an early stage company in an emerging market.  Almost every presentation I’ve seen has a market size section.  Almost every market sizing presentation is incorrect – by a lot. Enough to make it irrelevant. Most of the companies I invest in are in markets that are early in their life.

My immediate thoughts turned to asking those in the other camp–the TAM matters camp–why and how they evaluate this concept. Can you ever really predict how the market you are in will develop and make accurate projections solely based on your target audience?  Would love to hear your thoughts.