Every implication of distrust, every bit of withholding and not sharing of ones ideas and feelings stands in the way and has impact. Often it gets introduced early around the issue of how the team will handle authority and leadership. Though groups often don't understand it, their decisions about leadership involve decisions about how influence will be shared, the flow and directions of communications, how priorities will be coordinated, and especially, the depth of commitment and responsibility to be called for from each participant. Genuine teamwork, especially where the work of the group is personal development rather than the development of some rational product, calls for strong commitments to contribution from all members and is usually facilitated when leadership decisions are postponed, and minimal leadership differentiation emerges based primarily on contribution to the specific task as hand. Tasks vary over the life of a group and so should leadership.
Proactive teamwork requires unified purpose and pretty uniform contributions.
It takes an attitude of willingness to take full responsibility for creating fully shared and collaborative processes where every element and aspect of decisions is open to challenge and question. The kind of accountability we're talking about here is largely one of taking responsibility for oneself, not taking responsibility for others. The lack of open data about feelings and perceptions in natural work groups is frightening and confusing. People who are trying to 'go along' in order to 'get along' usually make messes of things since decisions get made that nobody has any investment in. Integrity and candor are among the most difficult challenges of leadership and personal development - and the most important prizes of a strong commitment to personal growth.