Contributor by Google is the latest attempt to get people to pay for web content.
People register (currently you can join a waiting list), agree to pay a monthly amount, and then this is split between the participating sites you visit over the course of the month.
In essence it's a new version of Flattr, which was created in 2010 (& is still going), but with the Google version the sites you visit become ad-free, with the ad space replaced by a 'Thank You' message.
It's being labelled as an experiment, but I can see this working given Google's size and power - think of all the sites that get revenue from Google AdWords. Think also of how much advertising rates have fallen - sites that get 5% of your $3 a month would probably make far more out of you than they would from the ad impressions that you generate. Other sites (like this blog) would far rather take payment this way than take the teeth whitening and belly flattening ads that plague some corners of the web.
I'm assuming that Google will take a small cut of the fee (nothing wrong with that), and it's interesting that this has been announced in the same month as Music Key, a paid programme (also in beta) to let people have an ad-free version of YouTube.
As time goes on I think the paid model will do well for many sites, specifically (maybe obviously) those that have users willing and able to pay. The brainier sites perhaps, like Metafilter, that currently has over 3,500 visitors voluntarily funding it.
You could also argue that this could bring about a whole new of clickbait, if it's based on a visit, rather than time spent or a deeper engagement, although people would get wise to this.
One final thought - imagine how valuable Google's list of paid ad-avoiders is going to be - people who both have disposable income and can't easily be reached with standard online ads...