See thread beginning at http://gcc.gnu.org/ml/gcc/2012-04/msg00521.html and in particular the response at http://gcc.gnu.org/ml/gcc/2012-04/msg00677.html which identifies the problem and proposes a solution
Adding overseers@ to see what their input is.
I think this was fixed by periodically culling user accounts that have never edited a page (which removes all the spam accounts that get created).