I have figured out what has happened to him. He has added a user name "[unassigned]", you can check his friends list and see.

What happened to this guy???

I have figured out why this is happening
1. Its is because if you added somone named unassigned or either just created an account that only has Dota 2 on it and a small playtime on it
2. You could have also downloaded something

ok

I have experienced these things before from other people. But I knew better

Going to confirm what Purge said below. Going to block until this is fixed, if ever.