You don't need to trust whoever that is going to have a deal with you because we have some reputable escrow on this forum, as for the gift cards thing, im not really familiar with either starbucks or amazon gift cards.
How can I be sure that the person who is the escrow hasn't sold his account? The person will say that I need money and so I sold my account and his gain will lead to so many people losing their hard earned money.
That's what I'm trying to say that one wrong act of selling/buying accounts leads to so many wrongs here.
You can ask a signed message from a "public" bitcoin address or if you want another
also the pgp signed message.