Freeloaders will always be around. there is no way to get around them. Even if you were able to use a block sooner or later someone would find a way to bypass it. There is no true way of fighting them either. Most freeloaders are not going to even bother to use a forum like this except to insult people. Do you think they really care that they are freeloading, because they don't. All they think is, "Hey! I got me this file, ahuh, ahuh!" If they are too selfish to share their files they what makes anyone belive that they care what they are thought of.

As for the 20gigs thing, I am willing to bet there are several out there who have this much alone in a computer. It is not unlikely for this to be true, however there are just as many who do not have that much and still are sharing what they do have. Personally I have no ****ing clue how much I have but I have put all but my extremely personal stuff up for sharing(ie family pictures,programs with personal information) and I am going through my computer looking for anything I might have missed.
But to deny access to someone who has a limited amount of files available but to take from them is almost as bad as freeloading. You are in a way doing the exact same thing to them as the freeloaders are doing to you now.