If Jason Giambi doesn't cooperate/testify before the George Mitchell steroid investigation, he will almost certainly be suspended by major league baseball.
There are two schools of thought on the Giambi suspension. Many reporters and more morality-minded folks see it as a brave move for Selig to finally bring someone down in the "battle against steroid use." I hate to pick on Buster Olney again, but he is one of the more prominent members of this particular lobby. In his blog, Olney claims that "The finish line for a seeming public relations victory is in sight for commissioner Bud Selig."
There is a second school of thought among the columnists and the more sabermetrically-inclined that such a move would not only be a useless display of confused morality, but would also be counter-productive. Olney doesn't see it as a case of confused morality (at least not that I've seen), but he does address the fact that the commissioner's move may be counter-productive. Viz: