These methods for Building Trust are true across any medium, whether face-to-face or online. A good indicator of trust-building online is Online Dating. The History of Fraud shows that fraud existed long before the Internet.
Trust is part of Social Capital.
Some people in some situations require "high-touch" in order to build trust. See Group Archetypes.
The Trust Trap
Psychological research shows that, once we trust a source, we are not only less likely to scrutinize information from that source, we become more susceptible to being tricked into false memories, even in the long-term.
On the other hand, when we get burned, we tend to have an overly cynical attitude about whether or not we can trust people.
How do we reconcile these two psychological traps?