I'm not Azevedo would consider this one of the resources, but I had a hard time thinking of anyone who legitimately belongs in a community of practice who would say that there is just one "site" in which he practices it. Depending on where Mitchell is -- and even when he is in his home -- the activity that he engages in differs, but since he is always an astronomer, he engages in astronomy in different ways depending on the site that he is in.
I can consider myself a golfer, and certainly I "play golf" on the course. But I exercise my "golfer"-ness at the bar when I'm watching games with friends, online as I contribute to forums on instruction, etc.
I think it is interesting to contrast this with how we see kids and school subjects, for instance. For many, the classroom is the beginning and the end of how what is taught there permeates the rest of their lives.