Basic questions:
1. Where is the data stored? How much redundancy? Obviously you need data to serve content.
2. How do you ensure that users are actually serving the correct data?
3. How will you validate the amount of data being served? (Imagine that an attacker controls both sending and receiving nodes. It would be trivial to fake the amount of bandwidth "used").
4. What types of data will you disallow? (This has many important legal consequences, as I'm sure you can imagine.) If everything is "allowed", I'd imagine most users unwilling to participate in fear of lawsuits/retaliation/subpoenas.
5. What is a "coin"? (unit of storage/bandwidth?) What is "difficulty"?
3. Nodes cannot cheat the system because there are multiple nodes sharing the same file. The node that the user connects to is chosen at random.
Edit: Decided to go ahead and answer number 3.
I assume this is a torrent-like scheme where files are broken into independent, verifiable (by hash) pieces, is that correct?
Storing data in nodes seems to assume unbounded storage space. How will you make sure that nodes actually have the requisite storage space? Particularly important for high bandwidth, storage constrained systems (I'm talking about VPSes, of course, which will probably be the source of the majority of the bandwidth).
It seems like this could be used for nefarious purposes (I'm talking about DDoS); will there be measures to control how many coins a potential attacker can get and/or use at the same time?
It also seems like at least in the beginning, the system will not come close to even saturating bandwidth. In that case, what determines who gets block rewards? Random chance? Latency?