Trust is a rare commodity in EVE Online, and is one of those aspects of the game that makes it at once interesting and frustrating. That friendly person who offers you assistance in a mission, wants to sell you a faction module, or seeks to join your corporation may very well be waiting to backstab you when you least expect it. This might sound bad, but it's not necessarily a terrible thing in terms of enjoying the game. Indeed, some may feel that it adds to the risk inherent in EVE, and thus the thrill. The fact that players can manipulate trust within the rules of the game is one of the aspects of EVE that sets it apart from most other MMOs.
The risk vs. reward stakes are raised when trust comes into play with groups of players. Collective action through corporations or alliances will, at some point in time, entail trust. It may be a CEO or director lifting restrictions on access to resources for a member of the corp, hoping that the faith placed in the recruit wasn't a bad move. In other scenarios, the situation is reversed -- a director decides to cut and run, seizing assets and leaving the corporation shocked and understandably enraged.