My daughter frequents those cons every chance she gets. She's got some stories, lol. I don't know that it's frequent in the broader sense, but...absolutely, it does happen.
Yeah, I don't know about guests/panelists these days, but back in the 80's/90's when multi-day cons were still big, like Westercon and Norwescon, there was hankying and pankying all over every adult floor.