Just interesting reading about the concept of file sharing no point trying to be made.

From Wikipedia

There are several major issues surrounding file sharing. Of these, the two most important are centralization vs decentralization and the privacy and anonymity of users. The latter takes on added importance when the legality of file-sharing is challenged by some copyright owners. A third issue is the collection and sale of data about users, using software referred to by its detractors as "spyware".

In the early days, client software was protocol-specific, so one had "Napster" clients, and one had "Gnutella" clients. There is an everpresent push towards making the GUI-side of things capable of using multiple protocols. It is argued: why should a user have to load up several different applications to do what is, in their mind, the same thing?

In cases where there is perceived value in collecting, some people will have lots to share and will find themselves surrounded by eager people. This can cause problems when the collector cannot keep up with demand. Decentralization is one means to alleviate this problem, especially in cases where it is possible to ensure that multiple copies of a popular item are available from multiple sources (even simultaneously, as with multi-source downloading).

Decentralization has also been pushed as a means of overcoming the threats posed to a centralized network, either by legal disputes or hostile users. A decentralized network has no body to attack; only its individual active members may be targeted, and even if a small portion of them are removed the remaining peers on the network will still be able to function.

Concepts like leeching or hoarding come about where the one centralized person will collect files and later refuse to make those available to others. Trade and ratio systems evolve in order to reduce the impact of leeching. Under these systems, a person shares when he can expect to get something in return. KaZaA, for instance, has a very simple rating system. The client calculates the user's priority and tells the sources what level of downloading priority they should give that user. Shortly afterward, however, hacked clients were released that told the sources that the user had one of the highest priority levels regardless of his actual sharing.

Another client which has a rating system is eMule. The eMule client, which uses MFTP as its protocol, tracks how much downloading and uploading has been done from individual sources and if files are downloaded locally or if other peers download files. Sometimes it seems that this rating system does not have a big impact on the download speed. A reason could be the size of the upload queue and the chunk size. If there is a free upload slot, the client takes the peer on top, transferes 8 MB to it and moves it to the end of the queue. A peer with rating of x2 would have to wait to get an upload slot for only half of the amount of time of a peer with a rating of x1. Furthermore, after the client has received an 8 MB chunk, it should upload an 8 MB chunk to the other peer as soon as possible if there is a download pending for that user. Then the other client would upload one chunk to you and your download speed and the one from the other client will increase.

BitTorrent also has a very good share rating system. The download speed is slow if a client does not upload, but it can easily be the fastest protocol if the size of the swarm is large enough.

Today we are left with a slew of clients with functionality designed around making sharing files more effective, both in the real sense of uploading and downloading (like anti-leeching functions) and in the more ethereal sense of being bulletproof toward legal issues (as with anonymity and decentralization).

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A little common sense goes a long way

Later Grandpa