No, it's not an epic snub, or retaliation for being so darn good at everything. Variety reports that Jackman "quietly turned down the job" a few weeks ago. The reason is simply that he wants some time off in between A Steady Rain and production on Shawn Levy's Real Steel. Reportedly, he really does want to host the show again, but he didn't want to do it two years in a row. That's a showman for you. Give them just enough to have them wanting more, and avoid wearing out your welcome.
In my humble opinion, Jackman left some very dashing shoes to fill. Personally, I think Shankman should see this as the start of a new tradition, avoid a comedian, and pick the Tony-hosting Neil Patrick Harris (who's already rumored to be eying the gig). The Oscars are supposed to be all about Hollywood glamour, and what better way to celebrate that then to go old-school and musical? I'll take a jolly musical number over painful attempts to be political and relevant. What about you? What host can make the Oscars worth your while?