I agree with keeping them hidden. I suppose it wouldn't be as exciting to watch on TV then but lets be realistic... The people sitting at the final table didn't get there and they don't win by announcing or making public their playing styles or revealing their bluffs etc... So although showing the hole cards may not affect that particular game or tournament, it certainly educates opponents for future games that may be played. Doyle Brunson hasn't made his living by showing the world his cards!
Erm... actually, Doyle Brunson kind of has. When he first released
Super System there was nothing else like it on the market, and he copped a lot of flak from the other pros at the time for giving away their secrets. So in a lot of ways he showed the world more than just his cards -he showed the world how he thinks.
As for everyone else, this is a point I've made a number of times over the years: poker owes a lot to television coverage, particularly to ESPN's coverage of the WSOP. If it weren't for them, there would have been no poker boom, no explosion of new fish into the game, and chances are a lot of us wouldn't even be playing.
We have hole card cameras because it's better for television. We have the multi-month wait for the November Nine because ESPN wants it. And the same thinking applies to streaming the WSOP on a 15-minute delay. If that's what they want to properly promote the game, to get more people watching it and getting interested in it, then as poker player's we'd be idiots to argue they shouldn't have it.