OK, here's my 2 cents.
First, copyright owners have an absolute right to control how and where their work is shown, with only a very few minor(sounds like a man who digs coal, or a bird which mimics) exceptions outlined by statute in any civilised country. If you don't like that, make your own porn and release it under Creative Commons or similar licence. A few amateur exhibitionists already do, but there would be much less porn without the financial motive.
Second, the corollary of this is that you don't have a god given right to as much free porn as you can download. Everything you download free is there either because somebody has kindly gifted it to the world, or more often because somebody is illegally distributing material in which they have no rights. Complaining that your 'free' porn has been taken away is just pathetic.
Thirdly, porn producers are free to take their own decisions about when a little leakage is acceptable and when aggressive revenue protection is required. If you post a short clip from a site with a clear logo and maybe even a link to the originator's pay site, he might see that as good advertising and overlook the strict copyright infringement. FHGs, TGPs and porn blogs are just a formalised and contractually agreed version of this, so the site owner is unlikely to be too upset at getting the same advertising without the 50% revenue share
On the other hand, if you rip a whole site and upload it all to Rapidshare, the only person getting any revenue is Rapidshare; you can see how a porn producer might in that case be inclined to get the material removed asap and maybe even make a civil claim against RS for lost revenue. RS has to protect its position, and that means taking down material as soon as a complaint is received, regardless of the true legitimacy of the complainant. They simply cant afford to engage arbitrators and investigative agents every time a complaint is made to determine whether A: the complainant has a good case under copyright or any other law and B: the uploader has a legitimate defence under fair use, public interest immunity etc. RS would be out of business in a week if they had to investigate every claim, so they just pull the content instantly. If you don't like that, don't subscribe to RS. Just using Rapidshare as an example, the same applies to every other hosting company.
Bottom line; there's a practically limitless amount of 'free' porn on the internet, nearly all of it stolen. If the owner claims it back, you're still ahead, because there's still plenty more out there which hasn't been deleted yet.