While there are no vector sources in that list currently, it would be a good show of faith to the larger community and a good preparatory feature to have the GeoServices branch respect this list that as well, checking any user-provided URL against that blacklist.
Currently, http://api.openstreetmap.org/api/0.6/capabilities provides a list of regex-able URL patterns to block, so that a user does not use Google imagery to digitize, for example.
While there are no vector sources in that list currently, it would be a good show of faith to the larger community and a good preparatory feature to have the GeoServices branch respect this list that as well, checking any user-provided URL against that blacklist.
see https://github.com/openstreetmap/iD/issues/4164#issuecomment-317900751