For example, the mobile app ecosystem (the only large scale experiment we've run in online media since the web) started with a pay-for-use business model in the form of paid apps. While this worked for a while, it quickly gave way to free apps supported by advertising or other business models. Today, unless you are a game, it is almost impossible to build a business using pay-for-use exclusively. Reversing to a free model was forced by the low cost of entry into the market and resulting commoditization of mobile apps. You can't charge for something if a dozen other people will offer it for free.
I'm not a huge supporter of online ads and I do think the industry needs to improve. However, we continue to see that it is the only stable economic model for online media considering the volume and diversity the model needs to cover. Until someone shows something else working at scale, let's not throw away the only thing that is working.