DC Comics has gone variant cover crazy. Since the end of Infinite Crisis last year, we've seen no less than five issues of The Flash featuring variant cover artwork. Your copy of The Flash: The Fastest Man Alive #13 might feature the Black Flash or it might feature the Flash's empty costume. This week's All-Flash special is available in two varieties, with covers by Joshua Middleton and Bill Sienkiewicz respectively. Kelson Vibber has updated Those Who Ride the Lightning with a guide to those issues of the scarlet speedster's comic that were published with more than one cover. Additionally, Vibber's blog spotlights the holofoil-emblazoned centennial issue variants that DC Comics published back in 1995.
Update: ComicsPRO, a trade organization for direct-market comic book retailers, has released its first official position paper--and it just so happens to concern the use of variant covers to influence sales! Newsarama has posted the press release, and it's worth a read.