I've read somewhere that you usually say: be dissppointed in smb but at smth. Therefore, I've got a question. Can you be disappointed in smth and at smb? If anyone said something like: I was really disappointed in him, would it sound strange to you?
ReDS: I don't think you asked your question right, did you?

"... disappointed in him" is not strange.
"... disappointed at him" is strange.

Emotion: smile
Teachers: We supply a list of EFL job vacancies
You're right. My question was wrong. I've finally come to a conclusion that it's not worth posting messages at night when you want to sleep.

I meant - disappointed at him
- disappointed in smth
Beware midnight lucubration!