Argumentum ad verecundiam is Latin for, roughly, "appeal to authority." It is a fallacy and is usually used when the speaker is running out of solid ground in their argument very quickly.

Examples:

"Isaac Newton was a genius and believed in god."

"George W. Bush is a governor and believes in strict imprisonment regardless of the cost or discrimination."

"Bill Clinton is the leader of the United States and commits adultery."

"Einstein was a genius and believed in god." (ed. note: he didn't)

"Bill Gates is the richest man in the world and uses Windows."

"Linus Torvalds is one of the most well-known persons in the computer world, and he uses Linux."

Usually the speaker follows their appeal to authority with a "so it/he/she/they must be real/true/right/moral/the right choice" statement.

Many thanks to http://www.infidels.org/news/atheism/logic.html.