The general rule seems to be make them pointless, valueless and public.
Do not make "Here's how to do it yourself so you don't have to hire me, or even talk to me" videos. Do not offer them publicly. Do not offer them privately. Do not offer them to clients. Do not offer videos like that to prospects.
Do not make "How to never hire me to code" videos. Do not make "How to never hire me for CSS markup videos." Really, I suggest you skip the whole range of hiring avoidance subjects.
Next, I recommend against making videos for people who 1) Are not in the market for hiring a dev or designer 2) Don't have any money to hire a Dev or Designer.
I am pretty uniformly against making your life a living nightmare. Step one is don't target non customers who have no intention and no way of ever paying you. But that's just me. I'm unconventional that way.
Take a look at the 37Signals Getting Real "tutorial/book." No rails tuts. No PhotoShop tuts.
No HTML/CSS tuts. No PHP, no Postgre, no fad of the week Jquery tuts. No "how to" at all.
It's all "why to" tutorials. And you know what? They sell this.
A small rule of thumb: If people won't buy it; don't bother giving it away. Public. Private. No difference.
Public: Why to, especially "why hire us." Case history. Contrary to popular opinion this is not hype, doesn't have to be advertising, and can be very informative. But you can't make a video like that if the site has no purpose.
Private: User studies. A/B split run results, strategies and tactics you've picked up from customers actually using the sites, and in short anything not about the technical mechanics of the site.