Everything is possible! The question is would we want it?
I would not. You see, we all waste a huge amount of time just checking and waiting for new things to click, both here on Fanslave and numerous other PTC, bitcoin faucets, and whatever else is going to give you a fraction of a cent.
So you want our computers to do the same thing? It's just not worthwhile. The electricity used and your ISP charges are far more than you would gain from such sites. And your computer would be so busy that you couldn't use it yourself at a speed that would satisfy.
Anyone who has used a "browser toolbar" will know that they don't actually work as advertised. If you are sitting in Europe, you will miss all the US opportunities simply because of the time delay factors - and if you live in Asia, well you never see anything at all!
By the way, Clixsense heavily censors what gets onto their forums. So you'll only see the promotion posts and will never see any complaints!
Google already monitors our computers to the extent that the Internet would be at least 100 times faster if Google didn't exist. Do you want Mozilla doing the same?
Fanslave, to me, is a time filler for when I have nothing better to do. If you are obsessed with earning cents, you need a life!