Full Court - Link
Not sure if I agree with the stat, as obviously a player on the best team in the league will usually have the best plus/minus stat.
Not necessarily. If the best team in the league has the best point differential, then it would. If the best team were to win all of its games in really tight contests, then it would not.
Putting that aside, the stat is interesting, but not dispositive as to the "best player" argument. Anderson Verajao, for example, had the highest plus/minus number in the NBA in 2009-2010, as he played with LeBron James. Also, if a player plays a ton of minutes, even in blowout contests, the numbers could be skewed (e.g., a team ahead by a lot may not defend as much toward the end of the game, allowing the opposition to score and allowing plus/minus numbers for all players involved to be skewed).
I do like Clay Kallam's work, in part because he always has a strong point of view, but also because his pieces are well researched. Most importantly, however, if you know Clay personally (as I do), he is always willing to listen to another person's point of view or evidence, consider that, and (at times) even change his analysis.
That being said, I personally think plus/minus is most interesting when paired with point differential numbers when said player is on the floor (on a per-minute basis), as well as the plus/minus for various lineups. For example, if Candace Parker plays most of her minutes with Kristi Toliver, the plus/minus numbers will be skewed. Keep in mind that Toliver is defending perimeter players, who are more likely to shoot (and make) three-point baskets, thereby adding to the plus/minus figure and point differential. If, for example, Parker is paired with Beard, DMJ, Nneka, and another guard, and her plus/minus figure is significantly greater, it certainly changes the analysis.
Another factor to consider is *how* the offense scores when players are in the game. Because Parker has such range on her shot, it frees up Nneka to score more inside and allows Alana Beard to drive from the wing (often the left side), as there is no crowding of the paint. When Parker is in the paint, it frees up players like Toliver to launch from three, because she demands so much attention.
But all in all, it is an interesting read...and offers one such statistic (though not a dispositive one) in determining the "best player" or the "most important" player.