Joseph Smith did it with his false prophecies. His nephew, Joseph F. Smith, continued doing it as "prophet" of the church. And in fact, prevaricated openly on the record in Senate testimony for the Mormon Senator Reed Smoot hearings.
Greg Call summed it up well in Times and Seasons (see http://www.timesandseasons.org/?p=1715)
Perhaps most difficult for the faith of the Saints was that in the face of heated cross-examination from the Senate committee investigating the Smoot issue, President Joseph F. Smith was perceived to have publicly dissembled, if not to have outright lied, about his knowledge of post-Manifesto polygamy. Even more disillusioning for some Saints was President Smith’s testimony to the Senate committee that “I have never pretended to nor do I profess to have received revelations. I never said I had a revelation except so far as God has shown to me that so-called Mormonism is God’s divine truth; that is all."
Amazing the effect that Section 132 has had on the mormon church leaders since it was "canonized".
"54 And I command mine handmaid, Emma Smith, to abide and cleave unto my servant Joseph, and to none else. But if she will not abide this commandment she shall be destroyed, saith the Lord; for I am the Lord thy God, and will destroy her if she abide not in my law."
Sure was handy for Smith to have had the "power of revelation" whenever it served his purposes.
I have to wonder what "revelation" will be forthcoming in the future regarding polygamy, since gay marriage seems to be in the cards for the nation...can polygamous marriages be far behind?