Well, my opinion (if anybody gives a shit about my opinion anyway
) is that people from 3rd world countries that can't join pay sites (they don't have credit cards, or are poor and don't have money for that) use rapidshare and similar services to share the files among them selfs (so they can jack off). Free porn (and software,movies,music etc.) attracts lots of traffic that can be used in various ways (many of them barely or not legal at all, but thats the other topic). Some of services similar to RapidShare even offer money for downloads so uploaders can even make money buy uploading and distributing illiegal content or content they do not own license for.