So, What's The Big Deal With Starting A Sentence With 'So'? 

"To listen to the media tell it, "so" is busting out all over — or at least at the beginning of a sentence. New York Times columnist Anand Giridharadas calls "so" the new "um" and "like"; others call it a plague and a fad.

It's like a lot of other grammatical fixations: Not everybody cares about it, but the ones who do care care a whole lot. When NPR's Weekend Edition asked listeners last year to pick the most-misused word or phrase in the language, that sentence-initial "so" came in in second place, right behind "between you and I" and ahead of venerable bugbears like misusing "literally" and confusing "who" and "whom." "

[NPR]

.... and the next politician who begins his answer to my question with "to tell you the truth" I'll interrupt with "do you mean you don't always?".   [clipper]