"Never judge a book by it's cover" springs to mind ;-) - you may find a thread that may look boring because of it's title, but if you read through it you'll probably see a good discussion going on. I always look at new threads and if it's one that doesn't interest me then I just don't post on it.
Sometimes I give threads a miss, but almost invariably check them out a day or two later to see if there is interest in them for me.
There are times when I wish I had checked sooner. I am beginning to ignore completely the "repeat" themes like cars, cyclists, Iraq, nasty Forum Editor, freedom of speech on SC, favourite tortoise name and so on.
I do not support the idea of SC failing through a poor choice of subjects, after all I could begin a thread and make a contribution but I do not, or at least not that often.