Lots. Stuff that can take you years to recover from. They can open credit cards or loans in your name, and put you thousands of dollars in to debt. Your credit rating will be shot, which means everything from getting a mortgage or car right through to a mobile phone contract will be difficult or impossible. They can use your details to escape crimes, and falsely charge them to your name instead. It can take years and thousands of dollars to clear your name, and all the time you will have a criminal record. They can use your details to help them avoid tax by charging it in your name instead of theirs, or by applying for a tax rebate in your name, again landing you in lots of debt that is very difficult to clear.

The fact that people are quite willing to risk all this for the promise of some worthless token is utterly mind boggling to me.