Hollywood filmmakers are getting served left and right by people alleging writers and directors stole their stories and made them into big budget movies.

Last week, a Croatian author filed a plagiarism suit against Angelina Jolie over her movie “Land of Blood & Honey," which opens this weekend. Days later "Avatar" director James Cameron was slapped with a lawsuit by a writer alleging that the blockbuster's plot was lifted from his own project. Even “Harry Potter” author J.K Rowling was summoned to a British court over claims she plagiarized a children’s book to write her series, which was turned into a box office-busting film franchise, and which also made her a billionaire. 

The case against Rowling was dismissed, but the other two remain, and there will no doubt be more. So do the plaintiffs in these cases have legitimate beefs, or are they just opportunists hoping for a big payday, or, that failing, a quick settlement to keep their mouths shut?

“You rarely see a lawsuit over someone stealing a bad idea and claiming it as their own while a film is still in production. Instead, lawsuits are filed only after a production company and all the people involved have proven its blockbuster success,” New York-based business litigator at Buchanan Ingersoll & Rooney PC, Kristi A. Davidson, told FOX411’s Pop Tarts column. “That said, there are many people in the chain of filmmaking, and it is possible that someone will run with an idea before making sure every t has been crossed and every i has been dotted. But that is far less likely to occur in big production houses with teams of lawyers papering every step.”

Sometimes lawsuits do bear some fruit for those who file them.

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In the 1990s, humorist Arch Buchwald walked away with $150,000 after filing a $6.2 million lawsuit after claiming that 1988 Eddie Murphy comedy “Coming to America” was in large part, his idea. In 2006, Chuck Wepner settled a three-year-old legal battle -- on undisclosed financial terms -- with Sylvester Stallone, after maintaining that he was the uncompensated inspiration behind Stallone’s Rocky Balboa character. 

Regardless of who wins and loses, the growing stack of lawsuits may be helping draw the line between a writer or director who draws inspiration from someone else’s story or real-life events, and one who unlawfully plagiarizes it.

“According to U.S. copyright law, ideas are free for anyone to use. Only specific expressions of those ideas are protected. So anyone can make a movie about a boy wizard who goes to school for wizards, but the law prevents someone from copying the specific expression in the ‘Harry Potter’ books, like the plot twists, the traits of the characters, the names and dialog. The line is grey sometimes,” explained Matt Belloni, news director at The Hollywood Reporter. “Hollywood is very sensitive about stealing ideas because of the long history of lawsuits. But the publicity surrounding the lawsuits does encourage other people who believe their ideas have been stolen to come forward. Unfortunately for a lot of these people, most of the cases are thrown out of court.”

But as long as a big payday is even a remote possibility, expect the lawsuits to keep coming.

“The profits and rewards of a successful film today can be higher than ever before, given the recession-proof nature of the entertainment industry and the multiple revenue streams from home video, online viewing and other sources,” added Los Angeles-based entertainment reporter, Scott Huver. “It would be naïve to think that there aren’t occasional, genuine instances of the outright ripping off of another’s story. But it’s so easy for opportunistic types eager to try and be paid off in what would be equivalent to a nuisance lawsuit. Some people will always be hoping to get settlement just to squash any bad publicity that could endanger the film’s overall profits.”