Traditionally it was pretty straightforward to protect material that you created: you automatically have copyright on it the moment you create it, and to document that you could register it with the copyright office, or the Writer's Guild, or even just send it to an attorney who would time-stamp it and put it in a safe place. If you signed a deal with a publisher, the copyright stayed with you and your contract spelled out what rights you were keeping or giving up or sharing.
The new media have made this a more complicated issue. Here's one example: I was looking for a place to host my podcast and ran across a site/service called MyPodcast. It's free and it looked pretty good, until I read the terms and conditions. Here is one of the clauses (stay with me through the terminology...):
"By posting content to any public areas of MyPodcast, you automatically grant, and you represent that you warrant that you have the right to grant, to MyPodcast and its members, an irrevocable, perpetual, non-exclusive, fully-paid, worldwide license to use, copy, perform, display, and distribute such information, rights of publicity, and content and to prepare derivative works of, or incorporate into other works and other media, such information and content, and to grant and authorize sublicenses of the foregoing."
OK, I'm not a lawyer (if you are, let me know if I'm reading this right) but I assume the "public areas" are all the podcasts, and that "members" are anybody who has their podcast on this service...and that according to this clause, they (or the people who run MyPodcast) can take stuff from your podcast and use it any way the want, including it into, say, a DVD or book they sell and you'd never see a penny.
Of course, MyPodcast is being honest about this (assuming you read the terms & conditions, which you always should) and for some people the free hosting might be worth giving up rights. But, to me, suddenly it doesn't seem like such a good deal anymore.
