I remember a factoid froma long time ago that women and politicians tend to use the passive voice more than men and non-politicians, mainly because of subject deletion: "Problem X will be solved." By whom? Anyway, I have seen any statistics or a formal write-up of the alleged phenomenon, but women and men I've mentioned it to usually nod their heads in agreement. Kinesthetics and proxemics are interesting adjuncts to anthropological linguistics.

If you're not familiar with the works of Deborah Tannen (at Georgetown U.), either her professional or popular, she covers the differences between feminine and masculine speech in depth.