I suspect one of a number of contributory reasons for people refusing to share files on the network are the "How to connect with LimeWire" blogs on the web. Almost all say "Do not share files under any circumstances" and to disable partial-file sharing, whereas I have seen at least one say if you choose to share copyright files then share them at your own risk. There are a lot of people who read these blogs and are no doubt immediately influenced by them.

Problem is, this means people are refusing to share files no matter what the status of the files. Where a person is sharing mostly or all non-copyright files, people are still refusing to share them after downloading due to the above type of influence and/or due to selfish arrogance.

If around or more than 99% of all users on the network are not sharing files, then it leaves a lot of pressure upon those who do share files.

Some gnutella apps allow a host to see how many files a host is sharing. It is amazing the number of hosts who don't share. The Lime based programs, particularly LPE and WireShare appear to be big culprits due to their larger numbers. But many users of all gnutella apps are guilty of "Freeloading" from the network.

People want something from the network yet are not willing to give anything back, not even the same file they downloaded.

Let's look at the torrent sharing world in comparison: I have seen torrents die within a month of posting because all who downloaded the file were freeloaders and refused to share back (seed) after finishing, thus totally destroying the entire share cycle.
You can see how 'freeloaders' can destroy file-sharing.

I have seen torrents where anywhere up to 250 hosts were stuck in an incomplete file download status of anywhere up to 99% of the file and unable to finish downloading the file.
Q: Who was to blame?
A: Far too many freeloaders not willing to seed (share) the file back to at least a ratio of 1:1 or higher.

So what is the solution?
Anybody wish to offer one?

Education of the sharing cycle and its importance might help. But how many people would really care.

Out of curiosity, who does more damage to the file-sharing networks? Anti p2p file-sharing BOTs or Freeloaders?

There is such a concept as private torrents. One thing a person can appreciate about that environment is knowing all are file-sharing and freeloaders simply cannot exist there.