I do think there is that same amount of fear of semi-solicited game proposals. A few publishers do actively seek game design documents from developers. However, in these cases, the legal agreement that you must agree to when submitting your game states clearly that 1) they could be working on a similar game, and 2) there is no real protection for the game developer. Submitting a design is just telling someone your idea, and there is no kind of agreement or protection (aside from copyright protection) for doing that.
It's not a lot of protection for a freelance developer... The problem is, I can understand why publishers are so shy of NDAs and such. In many cases it's just best to avoid legal issues altogether than to get into a fight which involves lawyers... One bad lawsuit at the wrong time could probably sink a publisher.
I am not aware of any publisher that would really try to screw over a developer. It's pretty dangerous, legally speaking. Not only that, but one or two bad encounters and the community will catch on.... It's a self-defeating business model. Of course, there is always the potential of a fly-by-night publisher that can really hose a developer, so I ~do~ recommend that you research who you may be doing business with a bit. A good place to start is the Casual Games SIG at the IGDA. They have a free whitepaper that talks a lot about the industry, and the major players.
The article was edited a bit from the origional version, where I talked more about the industry. The editors thought it'd be better to focus on my story, and less about the lessons I learned about getting a game published after I had goofed. I certainly respect their decision to do so, as it makes the article more targeted, and probably fits their audience better.
I think there are a lot of similarities between book writing and game design. By nature both are big, long-term, creative endevors. Though the medium is very different, the role of a publisher is pretty similar (albeit with a few extra hurdles). I also think manuscripts are like unfinished game designs. There are some interesting manuscripts out there, but finding them amidst the drivel is a daunting task.
Unlike books, games allow (require) you to define the means of interaction, which opens up lots of new venues for invention. Books, legally, are fairly simple. You have copyright protection, and that's about it. Of course, it'd also pretty difficult to disguise one book as another... By the time you've done that, you might as well have written the book from scratch. In games, I would say it's easier to plagarize game mechanics. Tracking down the geneology of ideas or interactions is a pretty daunting task. The controversies over the modern Graphical User Interface which involved Xerox PARC/Apple/Microsoft/etc. would be one example of the kind of conflict an exposed idea can create.
Blake