Forward deceleration using #include

Is it poor form to forward declare everything in its own header file, let's say "forwardDec.hpp" -- then #including that file in every other header file and just including any dependant header files from each of the .cpp files?

>>5
You should do it, continue using it throughout your large project, and then one month later come back here and submit a four page essay on why it should never be done.