Assuming the list of people in the memorium I found is correct, a lot of spaces to appear to go to people who were nominated or won Academy Awards in the prominent categories:

Abby Mann - 1 win, 1 more nomination
Anthony Minghella - 1 win, 3 more nominations
Charles Joffe - 1 win
Charlton Heston - 1 win
Claude Berri - 1 win, 1 more nomination
David Watkin - 1 win
Isaac Hayes - 1 win, 1 more nomination
James Whitmore - 2 nominations
John Michael Hayes - 2 nominations
Jules Dassin - 2 nominations
Kon Ichikawa - 1 indirect nomination (he direct The Burmese Harp, best foreign language nominee); also a major post-war Japanese director.
Leonard Rosenman - 2 wins, 2 more nominations
Paul Newman - 1 win, 9 more nominations
Paul Scofield - 1 win, 1 more nomination
Richard Widmark - 1 nomination
Robert Mulligan - 1 nomination
Roy Scheider - 2 nominations
Stan Winston - 2 wins, 6 more nominations
Sydney Pollack - 2 wins, 5 more nominations

So that leaves 9 people mentioned who I don't think were ever nominated:

Charles Schneer - Major B movie producer
Evelyn Keyes - Prominent second female lead in the '40s/'50s.
Joseph Caracciolo - Seems to have done art design and producing. IMDb doesn't even know he's dead yet. No wiki page.
Maila Nurmi - Better known as Vampira
Manny Farber - Prominent film critic
Ned Tanen - Former major studio head
Ricardo Montalban - Actor
Robert DoQui - Actor
Warren Cowan - Legendary publicist.

So it looks to me like they probably have some rule about which former nominee/winners are automatically included. Then they know they have X slots available for all of the other people who died that year and probably try to spread the love around a bit through industry.

And then hunker down for the inevitable barrage of "why didn't my husband get in!" complaints (I know this is real, some book on the Oscars I've read mentioned that many attempts have been made by producers to remove the segment so they wouldn't have to deal with the hurt feelings afterward).

Hmm...Well if Cyd Charisse was in there then the list I found wasn't complete.

Unfortunately the In Memorium page at Oscars.org is not a representation of who actually made it into the video. But looking at that list it does suggest that nearly everbody mentioned was a member of one branch of the Academy or another.

What a year!

From what I've seen elsewhere, this was shown on TCM, not the Oscars.

I thought it was this William Gibson

Both Cyd Charisse and Van Johnson were in the memorial.

And every time Strangler Lewis posts the Memorial Sucked, I feel compelled to post it was the Best Memorial Ever.

We thought the whole thing was OK.

I liked Anne Hathaway getting in on the opening number.

I liked the memorial. If I were his family I would have been unable to read the autocue.

I liked the way they presented the nominees.

Now we need to go back to the Kodak Theatre and pose on the steps again. :D

The memorial was the worst thing that was ever planned to happen at the Oscars. Indeed, from a taste standpoint, it was the worst thing ever done on network television.

Ok, the list I had found didn't include the first ten people in the montage. And it does appear that is where they mostly clumped the non-Oscar people). The complete list in order:

Cyd Charisse - Actress (no nominations)
Bernie Mac - Actor (no nominations)
Bud Stone - Executive (no nominations)
Ollie Johnston - Animator (no nominations)
Van Johnson - Actor (no nominations)
J. Paul Huntsman - Sound editor (no nominations)
Michael Crichton - Writer/Producer (a technical achievement win)
Nina Foch - Actress (1 nomination)
Pat Hingle - Actor (no nominations)
Harold Pinter - Writer (2 nominations)
Charles H. Joffe - Producer
Kon Ichikawa - Japanese Director
Abby Mann - Writer
Roy Scheider - Actor
David Watkin - DP
Robert Mulligan - Director
Evelyn Keyes - Actress
Richard Widmark - Actor
Claude Berri - Director
Maila Nurmi - Actress
Isaac Hayes - Musician
Leonard Rosenman - Composer
Ricardo Montalban - Actor
Manny Farber - Film Critic
Robert DoQui - Actor
Jules Dassin - Director
Paul Scofield - Actor
John Michael Hayes - Writer
Warren Cowan - Publicist
Joseph M. Caracciolo - Producer
Stan Winston - Special Effects
Ned Tanen - Executive/Producer
James Whitmore - Actor
Charlton Heston - Actor
Anthony Minghella - Director/Producer
Sydney Pollack - Director/Producer/Actor
Paul Newman - Actor

I like the way a technical achievement win ranks below nominations for an actress and writer.