As the web is mostly free today (I mean the old web, the one < 3), most people won't agree in beeing asked for fuel to run sites, apps, even if the gain in terms of safety and trust are so much more that what they could pay as fee to use Ethereum.
So what are the possible economic models to make Ethereum contracts free for use to user ?
I can imagine refunding but user would have to give fuel first even if they are refunded after they use it. I doubt that ads would be welcome on this sort of network, at least on its begining. I didn't see any way for the developper to preload contracts with fuel to make it free for the user (but I'm not sure it's not possible).
So I wonder how to achieve this goal. Perhaps I'm thinking the wrong way, so if anyone have tips to understand this part of the Ethereum.
EDIT: I know how to interact with contracts, I know about fuel fees, but my question is more about the economic model. I read about some model proposal on a blog post (I forgot where, sorry) that proposed refund and ads models. I also read about other crypto-currencies that implement fuel preload, but Ethereum don"t look to be this kind.
The only thing I know is that user (regular users, not geeks) will never accept to pay for something new even if better.
So what's possible to make Ethereum accepted by everyone as the web 3.0 ?