A few years ago, watching soccer on ESPN, I commented on the tendency of some sportscasters to provide commentary on things other than what was happening on the field. I found it distracting to my main purpose for tuning in, to enjoy the game.
I noticed the same thing today watching the ski cross event of the Vancouver Olympics. Guys are speeding down through the course and the announcers are all over the place. A little about what's happening, a little history, some comments on the course.
As Tom Ernst said about the World Cup broadcasters back in 2006
The main announcer should be like a good ref: keeping things going unobtrusively, helping out, and keeping order, but otherwise mostly unnoticed. These guys ... say things that the color man has to correct, repeatedly come back to minor themes like the weather or a player’s torturous path to MLS or where so-and-so used to play -– stuff we might like to hear once, but not 3-4 times, when there are so many things to say about the game (or just shut up and let us watch).
If the announcers must say something, they should do it the way they do baseball on the radio.
If the announcers can't comment on what's going on, like Ernst said, just shut up and let us watch.