VESA is the standard for display panel mounting, and Apple’s desktop displays have supported it for years. Unfortunately, the completely redesigned and ultra thin 2012 iMac can’t be legitimately mounted, according to a comment from Apple given to MacTrast.
“The new iMac is not VESA mount compatible at this time,” an Apple representative said. “We appreciate your feedback on this feature and will take it into consideration.”
Apple’s own VESA mount adapter kit actually notes incompatibility with the 2012 iMac. The $40 adapter does work with 2009-2011 iMac models and Apple’s Cinema/Thunderbolt displays.