* Barry Warsaw <barry@debian.org>, 2013-10-11, 11:03:
The point of this recommendation is so that missing Build-Depends are exposed when you are testing your package builds locally.
ACK
If you omit them, your package will still properly FTBFS, but only on the buildds.
Unless something changed recently, Debian buildds don't block Internet access. :(
-- Jakub Wilk