Many of the businesses that submit applications to TechStars have no clue how they’ll ultimately make money. In the age of free web services, many generically cite “advertising” as the revenue model.

Yesterday NPR interviewed TechStars founder Brad Feld, Kevin Rose (Digg), and Chris Anderson (Wired) in a piece called “Who Pays for Our Online Lives?”

In the interview, Brad talks about the various models for making money on the web in the age of free consumer services including lead fee models, virtual goods, selling access to consumers, and subscription-based services. It’s well worth a listen.