"These are the people that you have some type of intimate connection to. One study measured it as the people that you would send a family Christmas card to, while another simply tested emotional closeness.
In pre-Friendster days the Trust Circle would be those people that you considered your "friends", however today the meaning of that term has begun to change. In my own usage, your Trust Circle are people that you have strong ties to and that in some measure you can trust. I have also called the Trust Circle your personal "intimate social network".
The size of different individuals' Trust Circles can vary widely (40-200), but some studies show that the mean is on the low side of 150. This has led a number of researchers to compare this number with the Exclusive Dunbar Number of 150. However, I believe that this is a mistake; they are related, but in today's society members of your Trust Circle are rarely in the same mutual group."(http://www.lifewithalacrity.com/2008/11/personal-circle.html)