Uhm...first, everybody relax a bit. I'll turn this car right around if you can't behave.
Anyway, I object rather strongly to the idea that working for someone is slavery. Kirby could have (and did) produce other material. He could have left the industry. He didn't. Therefore, he was getting some benefit that, in a world where every idiot whose name we know is an oppressed folk hero or mustache-twirling villain by fiat, nobody wants to tell us about, because it spoils the legend (or because he never mentioned it). I guarantee it's not because he loved the people.
Before you accuse me of not knowing what it's like, I'm a programmer. I sit in front of a computer for eight hours a day producing code--innovating on demand, so to speak--for someone in exchange for a salary. The code is written on my employer's behalf, for the company, and they own the rights to every bit of it. I, on the other hand, don't. In fact, at my previous job, I was asked how I wanted code (which was to be released to the public) to be licensed, and I explained that it wasn't mine to decide, plain and simple. It has nothing to do with "work for hire;" it's just the deal you make. Why would anybody pay me to make stuff that I'll then own!? (And if you know why and who, why haven't you sent me their number?)
(Also: Everything in software is named after some guy, like there's some land grab going on, which is what I refer to above with folk legends--do you care that the Shell Sort was named after a guy named Shell? Does it help you understand how it works?)
I think that's appropriate and fair, because, if it becomes popular, it's probably because of the marketing muscle brought to bear, not my genius and artistry. Let's face facts: If Action Comics had been published by Nicholson-Wheeler as (I believe) planned, Superman probably wouldn't be much more known than the aforementioned Dr. Occult. If Siegel and Shuster had self-published, Superman would probably be as popular as Jon Juan or Funnyman. I imagine that most of Kirby's creations, likewise, would have fared about as well as Silver Star or Captain Victory, without the backing of Timely/Marvel or DC. If it weren't for shrewd (even if unethical) businessmen pushing the product, none of these trademarks or copyrights would be worth a thing to anybody!
However, as a human being, you're perfectly free to refuse to work for anybody who doesn't grant you the rights you want. If I wanted partial ownershiip of my software, I could actually semi-successfully approach prospective employers and find such a position. If I wanted full ownership, I can sell it myself...and I do, in fact, run a small business where I do exactly that, but that's more about me not being able to find a position where I can pursue those ideas than about me owning them. It works just like shopping around for flexible hours, a higher salary, fringe benefits, or any other "perq."
I won't say that you shouldn't believe as you do, of course, but you do need to understand that a lot of people see the "loss" of rights (to something you might not have created otherwise) is more than a fair price to pay for a paycheck and being able to skip past the part where you build your own business and distribution infrastructure to get your work (and your name) into the hands of appreciative consumers. And there's absolutely nothing wrong with making that decision or with a company holding you to that decision if you later decide you shouldn't have traded ideas for rent.
There is, however, a problem (in my eyes) with kids trying to convince the country that the big bad company owners are evil and should be punished for, y'know, having upheld their end of the bargain and profited by it, and that they, instead, should be allowed to make gobs of money from something that they had nothing to do with. (The endless copyright extensions and reclamation laws are going to bury this country in lawsuits and stalled innovation, as far as I can tell.)