Amidst all the comment on the Martha Stewart case, I think the most important point has been missed: the law under which she was convicted is a bad law. I don't mean the securities laws--- that malicious and silly charge was kicked out by the judge. Essentially, what she was found guilty of was lying to policemen. I don't think that should be a crime-- and certainly not with a five-year sentence.
On the statute in question, 18 USC 1001, the "False Statements Act," I highly recommend my former colleague Peter W. Morgan's article, The Undefined Crime of Lying to Congress: Ethics Reform and the Rule of Law, 86 Nw U L Rev 177 (1992). The False Statements Act reaches more (a lot more) than just lying to Congress, and his article surveys its history and some of its abuses.
Eugene Volokh has more: "Cases such as Martha Stewart's may discourage people (even innocent people) from talking to federal authorities at all, because they might fear that some error on their part may be characterized as a lie, and might thus mean criminal punishment."