(or "The Dreaded Reboot")
Even its detractors would have to admit that the James Bond film series is a genuinely astonishing achievement. Even the most popular movies die off after five or six sequels (horror icons like Freddy and Jason managed eight to ten), but James Bond's 22nd "official" film is in theaters now, and they're already getting started on Number 23. The series really does seem to be an "evergreen" franchise, having outlasted five of the actors who played the part (not counting the Niven Bond, the Sellers Bond, the Woody Allen Bond...) and the author who wrote the series of books it was based on.
Of course, those same detractors might also argue that the Bond movies are more of a formula than a storytelling engine; after an exciting opening set-piece, Bond meets with M and learns of some threat to the free world, then goes and gets interesting gadgets from Q (an element played down in recent movies, as the real-world spy technology has essentially caught up with Bond's MI6 boffins). He goes off and investigates, meeting beautiful women, getting into an exciting chase and evading at least one elaborate death-trap, before fighting the villain in an action-packed climax. That sums up the plot of most Bond movies and books (although it should be noted that Ian Fleming's novels were far less gadget-heavy and more cerebral, playing to the strengths of the printed page instead of the big screen.)
But the Bond formula offers plenty of flexibility; as a jet-setting spy, he has his choice of world locations from Jamaica to Russia to New Orleans, and "chase scenes" and "death-traps" and "gadgets" can mean anything from le parkour foot-races to elaborate space battles, depending on the particular era of the series. Bond films don't so much follow a formula as create one; our whole popular perception of the "spy movie" is moulded by the Bond films, whether imitating them, spoofing them (yes, hello, there, Austin, in the back) or reacting against them, as with John le Carre's spy novels (which have themselves been adapted for the screen.)
The flexibility of the Bond formula for the writer, though, is different from the flexibility of the Bond formula in the eyes of the audience. Writers might insist that there's always something new to be done with a glamorous super-spy who needs to save the world from a crazed madman's evil scheme, but when the audience stops being able to tell one Bond film apart from another, it's time to employ a strategy loved by some and hated by others: The "reboot".
Reboots are generally employed very late in the life of a storytelling engine, usually after the engine has been partially or totally ruined by bad writing decisions that have crippled its ability to function. Either so many elements have been added that only fanatical followers of the series can understand all the layers of complications obscuring the original, entertaining core concept (the Superman Emergency Squad, the bottle city of Kandor, New Krypton, super-pets, and a dozen types of Kryptonite) or else too many important elements have been destroyed/permanently altered due to a lack of foresight on the part of the writers and editors (the deaths of the Joker, the Green Goblin, Harry Osborn, and the lead character and entire supporting cast of 'Aquaman'.) Usually, the blame for this lies with the editors; writers tend to have their hands full thinking of story ideas (that is, after all, the point of a storytelling engine, to help the writers think of ideas) and it's the editor's job to evaluate their impact on the series.
The point is, when the series gets so completely written into a corner that you can't tell any more stories, you "reboot", starting over at the beginning, clearing the decks of all the baggage that's accumulated over the years, and going back to the core concept. Long-term fans tend to dislike it, because the root word of "fan" is "fanatic", and fanatical followers of a long-running series tend to enjoy all the baggage as much as they do the core concept, but a well-executed reboot can win over skeptical fans. It also tends to bring in new fans, who relish the chance to get in on the ground floor of the next generation of the series. (Of course, that next generation will usually have baggage of its own, not to mention the problem of new writers who try to bring back that old baggage because they're fans themselves--Ultimate Stryfe and Ultimate Onslaught, anyone?--but a reboot at least offers a chance at some fresh stories.)
But how does that relate to James Bond? After all, there's no complex continuity in the Bond films--they've changed lead actors five times, and nobody except George Lazenby noticed. There aren't any damaging decisions to undo; every Bond film is pretty self-contained, sharing very few recurring characters...unless you argue that the introduction of John Cleese as "R", or Felix Leiter losing a leg are "damaging decisions", really, any Bond film can serve as an introduction to the series. Even the chronology is loose, vague and unimportant to the films; Bond has moved from Cold War politics to a post 9/11 world, and all that's changed is what country the villain is working for.
A soft continuity demands a soft reboot, and that's exactly what "Casino Royale" is; it doesn't so much erase the previous movies as gently ignore them. It could be a flashback--after all, Bond movies seem to take place in a sort of ever-present "now", so a flashback film that seems to post-date the movies it's set before seems kind of appropos. It could be a reboot--sure, M is the same character as in 'Goldeneye', but Bond films have pretty short memories, so why not? It could just be another stylistic shift, the same as occurred from 'Moonraker' to 'For Your Eyes Only', or from 'A View To A Kill' to 'The Living Daylights'. Since the Bond films are fairly chameleonic in tone (as all long-running series tend to be), it's not too surprising to see shifts like that.
Ultimately, the much-debated Bond reboot is really just another way for the series to adapt in order to stay relevant, something all truly effective storytelling engines do. Times change, and a timeless series isn't so much one that fits the changing times as one that changes with the times. Daniel Craig is the Bond that fits this era; he's a rebooted Bond, yes, but in a sense, they all are.