I think phone calls can be good opportunities to learn about the other party, and they can go a long way to establishing trust. When I am speaking with someone interesting, I tend to be chatty, and having a good conversation can be helpful in establishing trust. That being said, when it comes to negotiating the sale of my domain name, establishing trust is secondary to establishing a price. Until we can figure out a mutually agreeable price, I am less concerned about trust, especially when the deal would go through Escrow.com anyway.