[IreneDelse]

A little caveat, here. Well, two actually.

1) First, the WGA are a union, because the Hollywood writers are not self-employed, like book writers, but rather are little wheels in a huge machinery. In a recent discussion discussion in the SFWA LiveJournal community, a very respected pro writer, Charles Stross compared book writers to "auto mechanics" with their own workshop" and the WGA members to the people who service the engines of an Airbus!
The WGA negotiates deals for all its members, just like a workers' union, and it enforces membership for aspirant professionnals in the field (you can sell a script in Hollywood without being part of the WGA, but if you sell a second, you have to take a membership). WGA strikes can stop the industry, or severely impair it, especially since the Actors' and Directors' Guilds often support the actions of WGA.

2) As a published novel writer, myself, I take an interest in copyright or "intellectual property" laws. And there is a fact a lot of writers haven't yet realized: when you sign a contract with a publisher for a paper edition, you very often sell the electronic publishing rights to that publisher also. It depends on what the copyright law is in your country, of course, and on wether you have an Internet savvy agent or not, but more often than not, the first stop for book authors who would like to go into e-publishing is their own "dead tree" publisher!