The number of users of TDD is simply too small to justify share ratio enforcement, at least at this point in time. etree has never done it because the community generally supports each other well enough to keep things seeded.

If by "etree" you mean "www.easytree.org" (aka EZTorrent), you're mistaken. They do enforce a minimum share ratio of 0.25.

I can't tell you how I know that without confessing my own blunders as a bit torrent newbie. The bottom line is, the policy bit me in the hindquarters and ultimately hurts the EZT community, too. Here's what happened:

I installed a Macintosh torrent client, miraculously signed up at EZT on the first try, and downloaded my brains out. I left the torrent windows running overnight. Next morning, only three of the seven downloads had finished but the network was down. I ended up rebooting.

Tried to resume downloads/uploads and hit the barrier: Access Denied because my share ratio had fallen below 0.25. Apparently my choices were not popular enough the night before, or the network died before my uploads ran long enough to keep me above 0.25.

Like a moron and/or newbie, I altered the downloads that DID complete, throwing out FLAC song titles or artwork I didn't want. Now I am stuck below 0.25 WITH NO WAY OUT.

Q. Why didn't you reseed some shows to build up your share ratio?
A. I could not, because my shows were incomplete due to deletions I made, before realizing the consequences. I had no other shows from other sources.

Q. Why don't you write to EZT moderators and ask for help?
A. I did. They repeatedly suggested that I seed new shows, which I repeatedly pointed out I could not do. They also suggested I pay money and become some sort of premium member, because then they would look the other way long enough for me to finish those downloads, keep them open to generate higher upload stats, and thus rehabilitate my share ratio.

Q. Well, at least have the decency to delete your EZT account, to make room for others.
A. I tried. It won't let you delete your account if it's under 0.25. Why this is, I don't know. I wonder how many dead accounts like mine are in that 100,000 total.

Q. Tell an EZT moderator that you're stuck in a dead end, so they can kill the account for you.
A. I did. He said it's impossible. My account will stay there until there has been FIVE MONTHS of inactivity.

Q. I hope you learned your lesson.
A. Darn right! For example, I left the Green Day torrent open for 5 days, until I had uploaded about 700% of the original. All other torrents I have left running until I was AT LEAST at 1:1, usually more than twice that. The reason I found this thread is that I was curious to find out what my share ratio has been at Traders Den. I'm sure my average is generously high due to my attitude and my big fat Comcast cable pipeline. I could be doing the same at EZT, but noooo ....