Watching a bad movie alone is way better than watching it with someone that doesn't get it.
That situation can turn out being a real drag. It's not easy finding like minded people.
I quite like watching bad movies on my own. I have and do watch them with friends from time to time, but some of them miss the point, so some times i prefer it.
There are definitely movies that are more enjoyable with a crowd - The Room, Troll 2, Birdemic, Manos, Miami Connection... The usuals. But, when you start to delve deeper, as I'm assuming most of us on this board do, it becomes harder to find like minded people to enjoy them with you. And, like Jay and crackers mentioned, if you're watching it with people who just aren't into it in the same way that you are (which, there's nothing wrong with that - it's an acquired taste), it takes a lot of the fun out of it for you.