In my humble opinion, I think the GHC should turn on ExtendedDefaulting if GHCi has it on by default. Otherwise it is confusing for newbies.
I think we're kinda tending in the opposite direction: we'd like NoMonomorphismRestriction to be the default unless operating in strict Haskell98 or Haskell2010 mode.
-- brandon s allbery allbery.b@gmail.com wandering unix systems administrator (available) (412) 475-9364 vm/sms