IMHO - If you ride in a group you take risks. If you ride tight in a group you take greater risks. If you pace line and close draft at high speed you take tremendous risks. I don't care if your riding behind Lance, anyone who tells you otherwise has never watch a multi-bike pro rider pile up. These guys take risks all the time - it's their job to take risks and push the envelope.
That does not mean you should not draft/ride in groups - it just means you must understand the risks and decide which to take. Make the simple corrections where you are managing your own personal risk level.
Every now and then we get a post bashing group rides/riders. Don't place yourself in a situation you are uncomfortable with, if you know how to use your brakes and steer your bike you don't have to ride with riders who make you feel unsafe.
We have had a few threads on how to act in a pace line, there is a lot of good advice in these that will help make the risks a little less - but don't ever think they go away.
Sorry - but that's my $0.02