From Deadline - 'Spider-Man 4'′ scrapped: (January 2010)
[...] Sony Pictures decided today to reboot the Spider-Man franchise after franchise director Sam Raimi pulled out of Spider-Man 4 because he felt he couldn’t make its summer release date and keep the film’s creative integrity.
[...] My sources tell me that Raimi told Sony Pictures: “I can’t make your date. I can’t go forward creatively.” And, so, once he said “That’s it”, Sony Pictures co-chairman Amy Pascal and Columbia Pictures’ Matt Tolmach decided they didn’t want to replace him and instead chose to reboot the franchise.
[...] The events that led to today’s shocking decision to scrap Spider-Man 4 can be traced to mid-December when I saw a December 11th email alerting the pic’s special effects crew that the fourquel would not be starting as planned ”but Sam Raimi has story issues [that] need to be resolved before we are ready to shoot”.
At that point, it wasn’t well known that the Spider-Man franchise director helming the 4th installment had huge problems with the script that has run through screenwriters Jamie Vanderbilt, David Lindsay-Abaire, and Gary Ross. I was told Sam Raimi had been very vocal inside Sony that he “hated” it.
(click the link to read the Sony's official press release)