Yes I have. My application to take the bar exam was stolen from the mail. It contained all the information needed. There are varying types of identity theft as well, from pretending you're a different person online to taking out new lines of credit in this person's name. There are, unfortunately no good types and hardly any resources being allocated to prevent this fraud.
To fix mine, I had to have a fraud alert on my credit scores. This way, no new credit cards, loans or lines of credit can be taken out in your name. I put verbal passwords on all my bank accounts and changed my online passwords and security questions for anything online. I also opened up a investigation with the FTC (877) IDTHEFT (877-438-4338). In the absolute worst cases, you can request a new SSN, but this will destroy any credit you've built up over the years.