Haven't nurturing this idea of trading a Bitcoin in the near future,but one question that's always come as a concern to me is. Is proper for me to trust a friend of that high magnitude ?
Is your trusted friend no longer trusted? Because including trusted in your topic means you don't need an answer, you won't create such topic if the friend is truly trusted.
If I have to exchange my Bitcoin with anyone it will be those in my circle, and I don't keep bad friends so I believe that I should be safe, although people change pretty fast this days.
It is still 10x better to buy and exchange your coins on a exchange because those exchanges will never sell you stolen or flagged Bitcoin, anything you buy on exchanges are clean digital assets.