ARIA: Why is role="marquee" necessary? We already have role="log"

Why is role="marquee" necessary? We already have role="log" in the  
spec. Currently, the draft vaguely mentions, "A major difference  
between a marquee and a log is how fast it gets updates from timed or  
real world events."

Unless someone has a good reason to keep it, I propose we ditch  
"marquee" and just use "log" for all instances.