Manny Farber died on Sunday (August 17th). He was 91. Here is a link to a wonderful piece by Jonathan Rosenbaum - written several years ago but revised and posted on the author's blog in tribute to Farber shortly after his death:
Rosenbaum on Farber
I hope to re-read Farber's "Negative Space" sooner rather than later, and after I do so I'll post some musings about it here (although Rosenbaum's essay seems so definitive to me that whatever I might contribute might just be superfluous).