A criticism I often hear about movies is that they are full of plot holes. But I wonder how many of these gripes are about genuine plot holes, and how many are more about the griper's lack of imagination.
A genuine plot hole is an inconsistency that is integral to making sense of the plot, but left unexplained. For example, in the horror movie Haute Tension (HUGE SPOILER ALERT IF YOU HAVEN'T SEEN IT), the twist ending is incongruent with some of the events that came before it (e.g., a person chasing herself in two different cars; a female getting a blowjob). It's not necessarily a flaw; people can debate what really happened and come up with perfectly good theories. But it's a hole.
But, demanding answers to questions the movie didn't even bring up, that's not an indication of a plot hole. Yeah maybe it's kinda weird that Harry Potter didn't just use the time travel compass thing from Prisoner of Azkaban to prevent all the horrible deaths in the later books. Why didn't he? Well, who cares? Make up an answer. Maybe it would be too dangerous. Maybe he's just a dick. Maybe Dumbledore dropped it in the shitter off-screen. It's not a question that's brought up in the plot, and it's not integral to figuring out what happened, so it's not a real plot hole.
My main point is that plot holes usually ain't so bad. At best they can make you think more about the movie, and at worst they're irrelevant.
That said, I just saw Southland Tales, and that movie is one giant plot hole. I've never before sat through an entire film and at no point had any idea what was going on. It was cool to see a bunch of comedic actors in semi-serious roles (Stifler looks like he's about to laugh even when he's crying), but really, it was just three hours of WTF. I'm sure some people will be motivated to watch it over and over again until they decipher it, but I won't be one of them.