[Haskell-cafe] Downside of -fglasgow-extensions

Hello, I'm trying to build diverse packages from Hackage with ghc 6.8.1, they usually fail to build because of missing language extensions. Sometimes I am unable to determine the proper name of the extension missing in .cabal I tend to slap {- #OPTIONS -fglasgow-exts #-} at the top of the troublesome file. It works, but out of curiosity, what is the downside of such an approach ? (bigger executables ?) Thanks M