I don't go to the cinema much, personally, so have never walked out of a film.
I prefer to wait until the DVD comes out, as then I can smoke, have a whiskey, eat junk food loudly if I feel like it, fidget in my seat without being told off by the pratt sitting behind me, go and have a wizz or answer the phone if need be and so on. I'm also spared the irritation of other viewers feeling the need to do the same or, and this is much worse, unleash a fart that shakes the foundations of the entire building while simultaneously setting off the nearest chemical weapons alarm. And they usually do this during the most important scene in the film, for some reason that still escapes me.
I'm also spared the ignorant twunts who, despite the entire big screen being taken up, before the film, with a short advert saying 'Please Turn OFF Your Mobile Phones', still insist on keeping theirs ON and, not only ruining important scenes by having the fucking Cheeky Girls 'Touch My Bum' blast out unexpectedly during the denouement (public execution would be far too kind, IMHO) then proceed to, instead of going outside the cinema, have a long (and unnecessarily loud) conversation ABOUT NOTHING IN PARTICULAR!!!!!!!!!!!!!!
Call me anti-social if you will, but I find the cinema as a social experience to be deeply over-rated.