Right, mentioning Keynote and services like Dropbox (as done in the article) in the same way isn't quite right. Yes the marginal cost for another user on Keynot

Right, mentioning Keynote and services like Dropbox (as done in the article) in the same way isn't quite right. Yes the marginal cost for another user on Keynote is zero but certainly not Dropbox or any other software as a service. If 2 people use Dropbox is may cost almost nothing but if thousands use it you either need a business model because costs could be significant or (like some of the big players) have another business group that subsidizes the running cost.