For God sakes yes I pay for porn and so should all of you. You still get higher-quality content from pay-sites, and DVD's on the home-theatre are hands down the best way to experience porn - especially when you do Blu-Ray.
But beyond a quality standpoint, you have to artists and studios you like - lest they go out of business. As of the past ten years skin biz has been producing works of art at a rate and scale that we have never seen before. The latest generation of pornographers and models have really worked hard to elevate pornography into something really wonderful and they deserve to reap the rewards of their work more than anyone so yes, I pay for porn.
I'm not saying it's "bad" to enjoy free sites and tube videos, I do all the time, but I regularly contribute to the cause. Oh and while I'm on a soapbox - support your local adult store darnit. Buy your movies down the street, not online ;-)