Limewire doesn't monitor traffic on the network. People are free to share whatever they want. That's the nature of file sharing and why there's a lot of spam/junk files being shared.
I don't think the freeloader option works. Just because you can't browse someone, doesn't mean they're not sharing. It could just mean that all their bandwidth is used up, or they are new and don't have any files to share yet. You'll have better luck browsing from your search results than form your upload window.
See LOTR's post for info on hash trees:
hash tree