An abridged history of Prohibition reads something like this:
A sad day on January 16, 1919 saw the the implementation of the 18th Amendment to the U.S. Constitution and subsequent outlaw of alcohol. Brewing companies, beset with tragedy and loss, consoled one another over cups of hibiscus tea filled mainly with their own tears (we're making this part up). Then, 14 years later, Prohibition was repealed and brewers cast aside those tea sets to grasp once more at a destiny full of barley, hops, and malt.
At Coors, a brewing company with history dating back to 1873, the repeal of Prohibition led to business as usual. But while the same company logo was easy enough to reinstate, nobody could find the original pre-1919 recipe and the (now ubiquitous) "banquet" beer was born.
In 2004, a brewer discovered an old logbook containing the pre-1919 Coors recipe (according to KDVR the book was rescued from a flooding basement). The company decided to test it out, and, liking it, began producing "Batch 19," a pre-Prohibition style lager.
To answer your question: yes, it seems like a gigantic marketing stunt. And when you consider Batch 19 isn't brewed according to the exact recipe, just inspired by it, eyebrows are likely to raise even higher.
Master brewer Keith Villa countered those claims in an interview with Metromix, explaining:
We didn’t have the same yeast, or the same hops or the same malt. Literally those ingredients have passed into history to be replaced with more modern versions. We tried to recreate best as we could the recipe that they made back then using modern ingredients ... The net result is a beer that’s very malty, medium-bodied, full-flavored with a really nice assertive hop character to it. We think it truly represents what they would have made and drunk before 1919 when prohibition put an end to brewing.
It's certainly a compelling story. And according to ratings, a fairly decent brew to boot. Reviews on Beer Advocate range from "a weaker American Pale Ale," and "a nice little beer in a Schlitz Gusto sort of way," to the all-telling "I'd order one again if the choices were limited."
An about-face by big brewers in recent years has seen micro-brew styles coming from MillerCoors, Budweiser, etc. Among these are Blue Moon, Shock Top, Batch 19, American Ale, Colorado Native, and a handful of others. Will the big boys co-opt the craft beer movement? Unlikely, though we're happy to see the little guys making waves.