This increase in communication (or openness) leads to greater trust by building a sense of community. When we offer to help out, we show compassion to one another. When we actually follow through and watch each other's home and babysit each other's kids, we show that we are reliable and competent to do the job. All of these demonstrate the ROCC of Trust. These aspects of trust, as studied by Aneil and Karen Mishra, have been shown to increase levels of trustworthiness between people, the more that they shared.
You can read about more ways to build trust in their new book, "Becoming a Trustworthy Leader" available for pre-order on amazon.com.