Yep. Clerks, for example, got an NC-17 which is fatal for movies - it's the same as our R rating, meaning noone under 18 can see it, and most cinemas won't even show the films, and most newspapers won't advertise for them, and the only reason it got that rating was because of the rather colourful language!
And it's not uncommon for movies to have a couple of naughty words to get a harsher rating so that people will be more willing to see it, because it's much cooler to see an R (American) rated movie than a PG. Oh, and the PG-13 rating was brought in specifically because of "Indiana Jones and the Temple of Doom" - no kiddies under 13 without parental supervision.