Actually, my feelings on the subject are that honesty is the best policy. I know that's cliche, but I think it might work here. The people who read the statements will probably realize that most of the applicants aren't entirely certain what they want to do after grad school, and that those who write as if they are certain are only writing like that because they are afraid that showing uncertainty in their career objectives makes them look bad.
To me, I think it is important to show that you are dedicated to making a positive contribution to science, whether that be in academia or industry. Sure, I can say that I think I want to work in academia, but that is far from certain. When I finish my degree, if I find that there are better opportunities to study the things that I enjoy in industry, then I will probably take a job in industry. You can say that right now, you think you would prefer a job in industry for whatever reason, but you are open to the possibility that during your time as a grad student, you will come to really like the academic environment, and so will decide for an academic career instead.
I guess I can't speak for anyone on the admissions committees, but I don't think that they would hold it against you if you expressed uncertainty.