I'm still trying to articulate for myself what I think about Billy Crystal's appearance in blackface at the Oscars.
The term blackface typically conjures up images of performers (both white and black) with caricatured African features in a style which in recent memory was best embodied by Al Jolson. Billy Crystal's performance was definitely not that, but it does bear a family resemblance.
One fact, which should be noted is that Crystal doesn't just have an isolated love for Sammy Davis Jr. but he is clearly really into blackface and the "performance of blackness" generally. For example, when he was on Saturday Night Live, in addition to his many Sammy Davis Jr. impressions, he did a short "mockumentary" with Christopher Guest in blackface as a retired ballplayer in the Negro Leagues.
Then on the Tonight Show, Billy Crystal did an extended impression/interview (thankfully without makeup) of Muhammad Ali, announcing that he was changing his name (again) to "Izzy" Chayim Yiskowitz and converting to Judaism.
I'm willing to concede that Billy Crystal is a well-intentioned person who doesn't mean to be racist but the same could have been said of Al Jolson. The issue with minstrely (in its old or new forms) is that every attempt at representation is ultimately a misrepresentation. By its nature, it is always a portrayal of blackness under a distorted "white gaze", showing us as they would have us instead of showing us as we are. (For example, in how Crystal's "Muhammad Ali" is made to become Jewish).
Perhaps more later...
Racialicious: All Things Old Hollywood: Blackface At The Oscars