There is a little bit more to the reason why the Mormon church is the largest source of genealogy data in the world. Each person who is put into a family tree that does not have their religion stated, the Mormon church supposedly accept into their faith, or something like that.
But don't let that put you off using their site. They don't push their religious ideals down your throat. They simply want you to use their site for recording your family tree.
Through this site, my family tree has been found to go back to the 1620's. My family has re-established links between my family in Australia, Germany, Denmark, England, Ireland, to the point where we have communicated with distant relative in America that we never knew we had. A relative who until the end of the cold war was in East Germany and since the fall of the Berlin Wall has been a fantastic source of information with regard getting birth, death and marriage certificates, that without the fall of the Berlin Wall would never have occurred.
geni.com has been fantastic in establishing all these links and relationships.