Two MB (the largest of our chapter files) is not a large file. The
compiled books are, of course, a bit larger (up to 10-12MB, as I
recall) but that is still not particularly large. The number of
illustrations is often large enough to cause display problem, but I
don't think that would be any different if the images were linked
instead of embedded: they still use memory when displayed on screen.
Linking has some advantages but it also offers lots of opportunities
for people (especially inexperienced volunteers, but even old-timers
like me) to muck up the files. I don't have the ambition to list all
the ways, but one is for people to fail to collect the latest set of
images when editing a chapter.
In a one-person shop, or in a well-supervised and well-trained team,
linking can be a good way to do things. For us, I think it's just
asking for trouble.
--Jean