I think that a lot of the people posting in this thread recently have a lot less knowledge of Avy science than they think they do. In this case I have to agree with CT Kook that trees do not automatically increase snow stability or your safety. I have no idea who CT Kook might be IRL, but in spite of all the crap he gets on this board he is often correct in what he says. I suspect that I might recognize his name if I was to hear it. I do know that we know a few of the same people IRL and some of those people are substantial.
I guess that I am about to get flamed for defending CT Kook. I don't care really, the fact is that I have participated in a lot of Avy training and studied snow science quite a bit. I have met most of the big names in snow science and talked with them. In some cases I was a student, in other cases I was a skiing partner, when I was really lucky I got to teach avy classes with them. I have taught several Avy1 and a few Avy2 classes throughout the inter-mountain region. During the winter I have daily interactions with numerous AK heli guides and the guide staff for JHMR. In fact at one time it was my goal to become a Heli Guide in AK. I cooled off on wanting to do this for a variety of reasons, but have lately been feeling that pull again.
I have seen plenty of avy debris in trees and even a few crowns in trees. As Ghost noted, some BC runs that people ski are only ski-able because a previous avalanche removed the trees from the slide/skiing path. I'm not interested in writing a dissertation about when trees become anchors vs trigger points, I will merely point out that the consequences of being involved in a slide are greatly magnified by the presence of trees. I love skiing in trees and will almost always pick a route that involves tree skiing, but the presence of trees is far from the only factor for me in choosing a "safe" line. I would also caution anyone about the whole concept of an "Island of Safety". I know at least 6 and maybe up to a dozen people who died in avalanche accidents. That number goes way up if you count the people who were on the scene of a fatality or who were captured but not killed. That number makes another very substantial jump when you look at people with one degree of separation from me. In fact I know two people who were on scene for one of the incidents that spawned this thread I can think of 2 very experienced people who I knew well that were killed when their "Island of Safety was overwhelmed by a slide.
I am not claiming to be some Avy guru, even Bruce Tremper and Dale Atkins would most likely back away from that claim, I am saying that I am an experienced BC user and have been for many years and have made an effort from the very beginning to learn as much as I can about snow, route finding, and rescue. My perception of these latest deaths is a bit different than that of a lot of the posters in this thread. Many of the people posting here are not really BC users and that is fine. It's a good thing to take an Avy class and read a few books. I think that extra bit of knowledge makes skiing more fun and interesting, even in-bounds. There is a big difference between reading a book and learning in the field.