There are solutions. I’ve just read (diagonally) a paper on attacks on Kademlia. The solutions would be similar to what’s recommended there. The problems are in appearances different, but stem from no admission control for the network.

All this tomfoolery about “or horror, how do we solve this” is because bot farms and recommendation systems and ad networks have proven very convenient and profitable, nobody wants to scratch that ecosystem in favor of f2f services. So they want to remove one side of the coin, but leave the other.