Ive been thinking about this and how to implement it, my conclusion was that NSA has the resources to filter out noise, especially seemingly random communication, as they already possess the social graph and have pretty good idea of who talks to whom and when. If suddenly a browser extension or app started sending "noise", to whom will it send it? A network? Where to get the list of IPs to spam? Just randomly? Just randomly is detectable! Thats easily filtered out - just exclude the network from the important data they tap. What if you randomly send a bunch of cat pictures and random noise to people of your contact list? This is called spam and receiving such, is not nice, as we can filter it on the receiving end, so can NSA filter it from their important calculations. But then you might think, lets send noise randomly and in the random noise let us communicate... meh, basically what a "P2P noise network" would do is increase the hassle and usability of computing systems for everyone involved but wouldnt really offer privacy for us.
When you kind of begin to make it less random, then you basically introduce plausible deniability and onions and begin solving problems that people are already working on and who need your help there more than "p2p noise network", then youre back to "lets make a good usable p2p anonymous/deniable communication system that can withstand NSA as advesary".
Still, it is an interesting idea, how to flood NSAs/FRA/GHCQs systems? Can we make a browser extension thats easy to use that would randomly GET pages from your history while you are actually away from computer - generating false content and increasing bandwidth usage, or a configurable spider to follow links/pages or even friends streams of choice? Would you use spammers techniques of markov chains to post random crap on open systems? Meh, thats still just an inconvenience for NSA.
What seems to be really important is who talks to who then how do you get in contact with strangers on the internet without NSA knowing? How would you know the stranger youre talking to isnt a cover agent?