The Byzantine generals problem describes the difficulty in creating a trustless communication system between a group of individuals. You canread more about it in this Wikipedia article about Byzantine fault tollerance -
Wikipedia onByzantine fault tolerance.
The article is fairly lengthy and complex, so you may want to skip to this video by Tech Cash House which discusses trustless payments, and why Bitcoin is the first crypto-currency to provide this benefit..
Here is what the pros say about Bitcoins future value