I'd hate to engage in a "they shouldn't have been out that day" discussion because most of us have done similarly in the past. Otherwise, it would be unfair to those lives lost to put the finger where we (or most of us) may have dodged 10s to 100s of bullets without knowing it.
It's easy to look back and use the Vail Pass avalanche and recent slide activity as omens to back away. Sure, those are red flags and things that would have (and did) keep me inside. But the greater lesson for me personally deals with mitigating risk and travel underneath a death trap more effectively (or no travel at all).
The group may have very well been mere feet away from being alive today. And then what? Just say how terrible a decision it was to be out there? Or take home a deeper meaning that we could all learn from? I'd rather learn from this accident and broaden my backcountry skills than to point blame at being out that day.