Several business models come to mind. This first is advertising, which ranges from MFA (Made for Adsense) pages at one extreme to Facebook at the other. Free b

Several business models come to mind. This first is advertising, which ranges from MFA (Made for Adsense) pages at one extreme to Facebook at the other. Free benefits for users come at the 'cost' of being exposed to ads. Then there are freemium models, where basic services and features are free, but additional ones cost money. See Dropbox as one example where the value to a user is increased if there are more users (Metcalfe's Law, though not really a 'law' as applied here) so the service has a free option, and the ability to pay for extra utility. I would group things like Farmville into this area as well - basic utility for free, pay for additional features, though some of these business models raise concerns for me in that the free utility is ultimately less than it appears at first (ie, you can't play Farmville the same way for free forever). A final option that comes to mind is the ability to leverage the users of one business into another. Bugmetnot built a large, free user base (indeed, it was built on the premise that people didn't like signing up for so many damn websites), but they then developed Retailmenot and successfully transferred the 'free' community into a 'paid product'. This is the hardest to get right, as there needs to be inherent value in both service offerings - if you only build the free with a view to flipping the audience, chances are you won't create an audience there to begin with. Any others?