Under the guise of giving advice for our own screenwriting projects, John August makes some good points about coincidences in the Spiderman 3 script.
He divides coincidences into two basic categories: Fundamental and Minor. The latter are often the result of oversight or slack writing:
My point is not to rip on Spider-Man 3, but to urge readers to look at their own scripts with an eye towards coincidence. If you’ve written a treatment, search for the following phrases: “at the same time,” “accidentally,” “luckily,” “unfortunately,” and “meanwhile.” They’re often a tip-off that you have events happening by coincidence. There’s almost always a better alternative.Multiple Fundamental Coincidences, meanwhile, are characteristic of the superhero/comic-based genre. [August is writing the script for Shazam.]
If we assume that almost every script has its genesis in a Fundamental Coincidence, then using the $258 million Spiderman 3 budget as a gauge, each additional Fundamental Coincidence in your script increases your required budget by $65 million and decreases the likelihood it will be produced.
Perils of Coincidence [johnaugust.com via tmn]