I don't know the whole story of what this man did, but the first thing that stands out to me is that he is nearing the end of his sentence. He has almost completed his time, and should just learn from his mistakes and move on with his life. What good is a pardon going to do if he is such a high-profile person anyway? It's not like people aren't going to remember him and what he did.
A pardon would mean he would be determined not guilty of his crime. I believe their is no question as to his guilt in this matter. He is nearing the end of his sentence, he could possibly be eligible for early parole. A pardon however, should not be an option.
No, the former governor of Alabama probably should not get a pardon. I trust Obama's judgment. He pardoned around 330 people. That he chose to not pardon this person probably means the former governor is guilty, with his actions doing harm. In any case, it doesn't matter too much since his prison sentence is nearly over.
If Siegelman is nearing the end of his sentence, it is my understanding that a pardon would allow him to continue his work in politics in some capacity. Not only does this encourage a politician who has been convicted of crimes to go back and do the same again, it will also send the message that others can commit the same types of crime and get away with them, at least as far as their records are concerned. To me, pardoning a politician on the merit of his office sets a very bad precedent.