...and the other person doesn't leave you feedback. 
I can't count the number of times this has happened to me. My latest purchase, the seller said he hoped we would exchange positive feedback after completing the transaction. I left him feedback right after I got the item, weeks passed and nothing from him. I emailed him today asking for him to leave me feedback, the bastard.
From now on I'm only gonna leave feedback after the other party gives me feedback.
I can't count the number of times this has happened to me. My latest purchase, the seller said he hoped we would exchange positive feedback after completing the transaction. I left him feedback right after I got the item, weeks passed and nothing from him. I emailed him today asking for him to leave me feedback, the bastard.
From now on I'm only gonna leave feedback after the other party gives me feedback.