Great article. I've been inaccurate in the blog saying that cache coherence will or should go away. What I mean is that ugly (non-scalable) effects of cache coherence as implemented by today's vendors can be relieved by Erlang VM to some degree. In the comment above [1] I say "It can also scale well if sniffing is not a broadcast". Your article is to the point by addressing exactly this issue with tracking of sharers.

[1] http://news.ycombinator.com/item?id=4780706