I've certainly thrown these numbers around myself from time to time (here and here where I get my facts wrong, for example). And I've found them to be valuable heuristics to keep in the back of my mind. It's nice to see that someone has pulled together and organized much of the underlying relevant work. It will be handy to have this available.
The Dunbar Number as a Limit to Group Sizes. Lately I've been noticing the spread of a meme regarding “Dunbar's Number” of 150 that I believe is misunderstanding of his ideas. (post continues with a discussion of Dunbar's Number, the size of groups, some empirical and anecdotal experience with sizes of groups. [Life With Alacrity]