Studios might be left dusting off scripts that have languished on the shelves for years to keep the production pipeline flowing, and the quality of the finished product would inevitably suffer.
"I would expect that as last time, you will see some forgettable movies coming to theaters," said Kim Masters, an entertainment correspondent for National Public Radio. "I can't see how studio executives can feel really comfortable going forward with a script where rewrites may be needed, as they so often are."
Steven Spielberg's "Indiana Jones and the Kingdom of the Crystal Skull," reuniting him with Harrison Ford and producer George Lucas for next summer's blockbuster sequel, has finished shooting, so presumably it won't be affected.
Yet even filmmakers of Spielberg and Lucas' caliber may want the luxury of last-minute reshoots to improve something that does not work in the editing room. If they needed to bring the cast back to reshoot something, they would be stuck with the words in the screenplay or letting the actors improvise.
In normal times, writers work with actors, directors and others to continually tweak dialogue and action.
"You want the original writer doing that," said Barry Josephson, producer of the current hit "Enchanted." "That voice is what compelled you to move forward with the project, that voice is what brought the director to the movie and the stars. So you want that writer."
Ad-libbing on set is common in Hollywood, particularly in comedy. But directors, especially those who are Writers Guild members, have to be very careful to avoid any coaching of actors that could be characterized as writing.
Hundreds of screenwriters, including directors such as Judd Apatow ("Knocked Up") and Bill Condon ("Dreamgirls"), have attached their names to a pledge on the Writers Guild Web site in which they vow to not write a single word "until all writers get a fair and reasonable deal."
The second name on that alphabetical list is J.J. Abrams, creator of "Lost" and the director of the new "Star Trek" flick, with a fresh cast playing Kirk, Spock and the other characters from the original 1960s sci-fi series.
Due out on Christmas Day, the "Trek" film began shooting in November and continues through March, without the on-set assistance of screenwriters Alex Kurtzman and Robert Orci.
Abrams is no slouch at writing himself, yet his hands are tied if he runs across something that sounded good on the page but not in front of the camera.
"J.J. Abrams, how does he not write?" Masters said. "I don't understand how a WGA writer can turn off the writing part of his brain. You've got people wedged between not wanting to have their work turn out bad and not wanting to undermine their cause."
Abrams' film is vital for Paramount Pictures, which is trying to revive the sci-fi franchise after 2002's "Star Trek: Nemesis" flopped and the last TV spinoff, "Enterprise," suffered early cancellation.
The picket line Monday outside Paramount took on a "Trek" theme, with guild members wearing T-shirts quoting a line from Spock: "Logic clearly dictates that the needs of the many outweigh the needs of the few."
One strike member carried a sign reading "Beam us down some justice."