Thanks for all the comments. I e-mailed the FA back and politely declined his offer. I will not not send the letter to HQ, though many of you do have excellent points regarding privacy issues.

The rapport between us was good, we mostly chatted about Thailand and my travels. He did asked me to come on back and have a chat later on, which I didn't because I wanted to watch the movie. So he compensated by coming to me and chatting regularly throughout the 4 hour flight. The thing is, through his interaction with me, I wouldn't be surprised if he asked for my contact info. What was surprising, however, was that he got it from the confidential survey. Anyways, thanks for sharing your thoughts!