For the last year and a half every single pair of pants I own tears/rips at the crotch area over time because of my thighs rubbing together. Every. single. one. It's fucking maddening, man. I'm at least trying to make it to summer without having to buy any more pants but I'm down to 2 pairs.
Just had that happen to me. I blame it more on the shittiness of the khakis than the swoleness of my legs. Sucks that I had just gotten out the car and about to start a shift. Had me covering my crotch the whole day.