It's probably not possible to track gratuitous uses of the word "definitely" with any accuracy, but they're definitely daily occurrences. Commenting on facts and fictions, the trivial and the tragic, people are definitely committed to their opinions.
You could grow old gathering examples:
"Rayna and Juliette are definitely composite characters."
The Defense Department "is definitely taking [sexual assault] seriously."
The author of a new book about Anne Boleyn "definitely does relate to the doomed queen."
"Giffords bringing together two former colleagues on gun violence is definitely more heartwarming than the other behind-the-scenes story, in which Toomey refused to appear at a press conference with Chuck Schumer."
"What happened in Arkansas [enactment of an abortion ban] will definitely encourage others to take similar action."
"There was definitely a split between us and the White House over Mexico" [regarding a former DEA informant].
Former Patriot Wes Welker would "definitely like to thank New England for the six years" and is "definitely excited about the opportunity" to play for the Denver Broncos.
It's hard to know precisely when "definitely" devolved into a verbal tic, but easy to guess why. People with definite opinions sound confident, assertive, imbued with self-esteem and devoid of self-doubt. They sound, or want to sound, like winners. The emergence of "definitely" as our go-to modifier is a tribute to our old tradition of positive thinking and our new culture of reality TV: "I'm bringing it -- definitely. I'm definitely going to win this thing."