Having a hacker over, risks?

[ohgeetee]

This sounds more like OP paranoia than any actual risk. Most people who are "very smart and knows amazingly lot about computers" generally talk more about what they could do rather than what they have actually done.

Tell your friend you're worried. He should take it as a huge ego boost and wouldn't bother your [censored]. If he flips out and goes off on you for not trusting him, he was probably planning on hacking your gibson.