Ok, he isn't, of course. But adjusted plus/minus statistics for the year show him to be. (Here's the link: http://basketballvalue.com/teamplayers.php?year=2011-2012&team=WAS)
This is really a post about the severe limitations of plus-minus stats in-season -- and about JaVale McGee, who the team very soon has to make a very big decision about. There's a lot to be said about McGee, pro and con, but I've been surprised at how much weight some people seem to be placing on his plus/minus statistics this year, which are among the worst in the league. (And I've likewise been surprised by the weight some people seem to be placing on plus/minus to evaluate other teams' players for potential trades.)
This post is simply to suggest that we shouldn't take these stats very seriously, even as "just one piece of data." They are notoriously noisy, and probably not useful at all when the data set contains just half a season (and arguably even a full season) of data. They're more reliable over two seasons or more.
McGee, for instance, had a very good adjusted plus/minus last year, according the source I linked to above. Has he gone from a well-above-average player to one of the worst in the league from this year to last? I doubt he was well above average last year, and I doubt he's one of the worst players in the league this year. And I very much doubt he's gotten worse this year. But that's what the adjusted plus/minus would tell you. Other players who've been league bottom-feeder in recent years, according to adjusted plus/minus, include Amare Stoudamire and Kevin Durant.
I won't make a long argument here, but if you want to see how much plus/minus moves around based on purely random statistical variance, I'd recommend this article: http://kenpom.com/blog/index.php/weblog/a_treatise_on_plus_minus/ (It's primarily about the use of the stat in college hoops, but he broadens it out to the NBA, and the statistical points are entirely transferable.)
I'm not a statistician, and it's possible I'm missing something big here. But I'm referencing highly reputable sites and authors, I believe. Curious to hear reactions