Reply #14: I found this really interesting article on another bear, it may answer

[Pepper32]

...your question


Believe it or not, this white bear is really a black bear. These bears are known as white spirit bears and there are fewer than 100 of them all on Princess Royal Island off the west coast of Canada.


"A spirit bear is actually almost an oxymoron, it's a white- colored black bear. It's not an albino, its a very rare double-recessive gene that allows this unique adaptation to occur," said Matt Reid with The Great Bear Foundation.

MORE...
http://www.cnn.com/EARTH/9511/spirit_bears/

UPDATE: According to this article that says, YES it is rare.

It's an animal so rare no expert in Manitoba has ever seen one -- an albino black bear cub. Yet there it is wandering the woods and fields near Chemawawin Cree Nation about 400 kilometres northwest of Winnipeg.

"Something like this doesn't come around often," said Keith Klyne, a resident of the reserve who has seen the bear in the flesh. "It was really interesting to see."

MORE...
http://www.mts.net/~dushanek/Albino.htm