Among other things, now you have to maintain a set of dummy targets. If you have a variable (possibly generated) that is basically

  A_MESS_OF_FILES := foo bar zot

You now have to create dummy targets for bar, baz, and zot and not forget to add them. Or maybe break it into

  MAIN_FILE := foo
  SUBORDINATE_FILES := bar zot

  foo: baz
    sudo make me a foo

  $(SUBORDINATE_FILES): %: foo