Teaching Jewish law to the blogosphere is Gil Student's job (I prefer parshanut and politics) but the previous post generated so much debate I thought I'd do some homework
In Iggerot Moshe, Choshen Mishpat 1:38, Rabbi Moshe Feinstein writes about a shul that was badly fractured. One faction complained that the Rabbi had changed the liturgy (nusach), cursed, and made intimidating and denigrating speeches. They claimed their Rosh Yeshiva had been insulted and that remaining in the shul was impossible. They wanted to leave and start their own shul.
Rabbi Feinstein responded that this was not allowed because it interfered with the Rabbi's livlihood (hasagas gvul) -the very same Rabbi who had made the shul so insufferable. He adds that separatists had violated the principles of darkai sholom (harmony) and lifnei ever (causing others to sin) and even required them to pay damages to the Rabbi.
Rabbi Ephraim Greenblatt, (a talmid muvhak of Rav Moshe) asserts that this ruling applys both when the Rabbi owns the shul, and when it is controlled by the membership, because the defection of the disgruntled members will deprive the shuls of dues and make it more difficult to pay salaries and other bills. He adds that leaving the shul implies a deficiancy in the Rabbi or the congregation and that only contentious people(baalei machlokes) would do that.
Rabbi Hershel Schachter feilded a similar question with a similar reply ruling that it is forbiden to establish a new shul unless it is a matter of profound importance - with a Reform synagouge given as an example. He also cites the Magan Avraham who says it is preferable to pray in a large shul than with a small minyan.