another thing to be aware of (and something companies are learning with their policies), having a policy and not strictly enforcing it (including to stupid 'zero tolerance' levels) is that you can get in legal trouble for not enforcing it, or for inconsistently enforcing it (you are accusing me of breaking this policy, but you didn't punish all these other people for doing the same thing, you are just using this as a excuse to punish me)
as a result, having a fuzzy policy can be a liability.