Remember, for a business to increase prices, they either need to do it in such a way that it's unnoticeable (read: slow inflation), or by offering a benefit in exchange. They can't just go, "lol now wot used to be frees now costs dollahs hurhurhur", because it'll cause them to bleed revenue when people say "uh no thx".
The conditional negative reinforcement is an idea, but I don't think it'd be very easy to coordinate, and an easy victor would emerge quickly from that little scuffle between businesses (i.e. who has the most money and asks for the least money).
It would have to start out, say, as a membership. Be a subscribed Yahoo! Member and all Yahoo! Owned Domains load 50% faster [somehow]! Or be a Google Subscriber and get membership access to these websites: Expensive site 1, 2, 3. Or be an AOL subscriber, and get a free puppy!
Then, after the success of such a campaign, the next round would be to have fine print stating that being a subscriber also means you lose/get restricted access to competitor sites. Then eventually, no sites outside the domains they own. Etc. But it'd be a long process and take many many years, gradually.
Take for example, Hotmail.
Way back in the day, when Outlook was hot-hot-hot and Hotmail was new-new-new, it was 100% free to join and 100% free to check your Hotmail account from Outlook. Then, gradually, they started trotting out "special" memberships, with "more" space and file transfer (when, in actuality, it was that the paid accounts had all the original benefits, while new [free] accounts got gimped benefits). After a while, they took away Outlook-access from non-subscribers. So while free hotmail still exists, it's a gimped-ass version.
I got a hotmail account in like 2002 or 3 (and maintained it to today). It actually has all the features of a paid account, because it's so longstanding. I opened a new hotmail account about a year ago, for an address to put on my resume, and low and behold: it was hard as shit to find the ".. Or try Hotmail free!" link, then I got offered a subscription every 10 seconds, then I got a gimped version with wayyy less file transfer and space.
It's all gradual, baby.