Tunnel Creek avalanche kills skiers:
The page I've linked to describes a party of sixteen excellent skiers who went on a trip where they easily could have known better. Three of them died. It's common knowledge that large parties increase the risk of avalanche, but the page described the group excitement which no one managed to override.
One skier was sufficiently uneasy that she avoided the danger, but she didn't speak up to discourage the group.
This isn't the most difficult sort of situation requiring rationality, but it's far from the easiest, either. Any suggestions or work from CFAR about improving the odds of speaking up when a group is about to do something stupid?
The article is heavily multimedia, with big self-loading animations-- it's gorgeous, but it's a bandwidth hog.
Anecdotally, I find that saying something meta, like "This is one of those situations where people have trouble speaking up, and then we just end up doing it even if people have doubts," makes it easier.
I was in a very similar situation recently. But it was a small group, and I wasn't the only one who had doubts, which also made it easier to say, "I don't want to do this after all."
Anecdotally, I find that saying something meta in a way relevant to the situation makes any social interaction easier. Even when it's about how to mention that using meta in social interactions can be very useful.
In fact, it used to be my first and most effective social tactic, when specialized approaches didn't work (or I didn't know any for the specific situation), for a long time until recently.