The Franchise is Dead, Long Live the Franchise
Reboots should follow the same rules as covers of songs. If you're going to bring something entirely different to the song, go for it. But if you're not going to change a thing then there just isn't any point.
Last time I checked, Spider-Man did this origin story just eight years ago, and was damned well received. What exactly are they going to change? What amazing new special effects have become available today that will make this new telling of the origin story profoundly more realistic? Look, Parker's a geek, gets bit by a radioactive spider, gets superpowers, becomes Spider-Man. There's a redhead, a newspaper, and struggles to maintain a normal life while fighting crime on the side. Do we really need another two hours to show this again? There are monks who have lived in silent seclusion for most of post-pubescence who can recite the Spider-Man origin story better than their Psalms.
More to the terrifying point though is the answer to the question: who do they expect to want to see this? It's one thing to reboot a franchise in which the starter film was badly received (like Hulk). If no one liked the original, there's no reason people wouldn't want to see the reboot if done right. But if the original is widely praised, no one will have any reason to go see the film, they'll already have a perfectly good version of the story sitting in their stacks of DVDs. And if the reboot hits screens as planned in 2012, then the only people who didn't get to see the original in theaters are those who were less than around seven years of age in 2002 when the original came out, otherwise known as today's fifteen year olds.
The only rational market choice that yields this decision is if Sony has decided to push the film exactly for that young teenage crowd, the ones who swamp theaters for Twilight. Touché, cruel universe, touché.