One of the most common ways I start a sentence is with the phrase "Um, actually..." I love correcting people and it makes me the worst person at any party. Though that isn't entirely fair. People tend to find the first tidbit of information fascinating, and then turn on me after the fifth or sixth.
I don't really understand why people react that way. Sure, no one likes being made a fool, but don't people like learning new and fascinating facts? Especially when it challenges your previously held beliefs?
You clicked on this page, so I assume you get it.