Should GHC default to -O1 ?

[Daniel Fischer]

On the haskell-cafe as well as the beginners mailing lists, there 
frequently (for some value of frequent) are posts where the author inquires 
about a badly performing programme, in the form of stack overflows, space 
leaks or slowness.

Often this is because they compiled their programme without optimisations, 
simply recompiling with -O or -O2 yields a decently performing programme.

So I wonder, should ghc compile with -O1 by default?
What would be the downsides?