I have not done a deal on ePack that was done via HI messages / posts.... so if that's what you're asking, then "no".
I have sent paypal to people, for their ePack cards though. Contacted via FB & directly on ePack. It is trust, as was already mentioned. If I'm sending you paypal, and you're making a lopsided ePack trade.... ultimately, one of us has to send first, and the other person COULD burn them.