...the decision to relaunch every title with a new #1 is inextricably linked to the decision to move all superhero publishing to digital. While it's easy to view it as a cynical attempt to grab new readers with a false "start," or say that they're throwing away decades of publishing history for a quick buck, consider that the new #1s represent not only a reboot of continuity, but a reboot of the publishing model. They're drawing a clean break not for the people coming into the stores, but for the much hoped-for new readers who will soon be following the entire DC Universe on their iPads and GalaxyTabs.
Make no mistake, this entire endeavor is focused on the digital market. DC isn't dumb. They know print is dying. They know they have no chance at beating Marvel in the print market, as years and years of examples have proven. Rejuvenating the characters (literally) and providing a fresh start all across the line isn't about a quick sales bump in the direct market; it isn't about the direct market at all. It's so that people logging into comiXology to check out these digital DC comics they've heard about don't see an issue number in the 900s after Action Comics and throw up their hands.
With regards to the continuity reboot, I doubt it will be as complete as people fear. The August DC solicitations promise too many continuations, and they definitely knew this was in the work. Solicitations for titles like War of the Green Lanterns: Aftermath and T.H.U.N.D.E.R. Agents promise more to come; Batman Incorporated #10 is concluding on a "surprise ending." In an interview with USA Today, Dan DiDio stated that while roughly three-quarters of titles will see a creative team switch-up, one quarter -- the books that are working -- won't be touched by the reboot.
There's no conceivable reason to mess with high-selling moneymakers like Batman Incorporated, Green Lantern, Batman: The Dark Knight and, well, other Batman titles, and to do so would be a huge mistake, especially since Grant Morrison's major Leviathan uber-arc is, alongside Geoff Johns's Green Lantern, the only major DC title with ongoing stories continuing past August. The Superman and Wonder Woman franchises, on the other hand, are in desperate need of a shake-up. J. Michael Straczynski absolutely murdered any narrative momentum those books may have had before.