I'm fairly confident that if you don't specify the full path,
and the CF server is configured to validate component paths (this
is an option in 8) an exception will be thrown.
I've made a habit of specifying full paths for these reasons,
as well as to avoid duplicate named component confusion amongst the
team.
To further accommodate this setup, we use a central API,
which is mapped for all the applications and sites. So we
instantiate things such as API.com.mydomain.service. The full path
for that component is always available on all sites and
environments.