I own a blog, but it's totally unrelated from my videos. I'm currently working on turning it into a portfolio website with all my videos embedded onto it. Then the blog side will be turned into a behind the scenes type deal. Where I will post examples of all the paperwork, scripts, treatments and also draw examples the setup I used, which would be a birds eye of the room, where the lights were located and where the camera and other equipment was positioned.
I thought this would be a good idea, I know a lot of people do behind the scenes videos, but a blog with all the examples of paperwork and such would give it more of a learning platform as students of starting out filmmakers would be able to see the sorts of things you need to sort out when creating videos.
But I feel blogs need to add something new. If I could attach files and such to the description of a youtube video I wouldn't need to create a blog for it.
Conclusion: blogs are a lot of work, if you aren't going to add something unique and don't have to time to keep it up to date, don't bother. They can also cost a lot of time and money to create and keep.