Who has an active site with *current* stats that are even remotely accurate? ....until then all anyone is doing is throwing stats out none of us can confirm to be the present truth. I am also leaning toward the 66% sharing at least 100mb - but I don't know for sure so *shrug*

Anywho, as far as 'freeloading' goes it is always going to be a problem and if a user doesn't want to share that badly - they won't.
Some things that help the sharing ratio are to do prompt during install if you would like to share files and do an automatic search. And additionally every file you download should automatically become shared to the network. There are many other things, but its up the the user and client to make sharing painless and automatic.