I gave that question a few tries but I feel part of the problem is the market being saturated by giants doing half the job. Another part of it is the lack of interoperability regarding file sharing between operating systems. I mean - a native right click>send to>user - native notification to the user with a solution to direct p2p download from that person. No software needed, seemless integration. Why is that so hard?
I really wish the big boys would give that a try rather than giving us toy-like features and price bump.