There are people who know full well that somebody has PTSD, and make a game of deliberately jumping out at them so they can laugh at the startle reaction. That is truly sadistic. I won't tolerate people like that in my life anymore.
Yes, PTSD does get thrown around casually. If somebody once fell down a flight of stairs, and ever since then they've been very careful on stairs, this isn't because they "have PTSD about it." It's because they learned a life lesson. I've read where it's become the latest fad diagnosis, and that upsets me because when that happens, it waters down the public perception of it, and people who actually have real, live PTSD are taken less seriously.