The warning for follow broken doesn't seem to work if a member of the team gets "out of range" (example: druids switching to flight form and one member of the team gets "stuck" on the ground). I can fly away to such a distance that the follow is broken and when I switch to the stuck druid he is no longer following but I never get a warning about it.

I do, however, get a warning if I switch to a team member while following and manually move him backwards (breaking follow manually). It just seems that when follow is broken automatically because of distance that the warning is not given.