Via Doc Searls, I found this piece by Kent Newsome. He nails the reason why blogging (podcasting, vlogging, etc, etc) aren't taking off in so many companies:

What I'm still not buying is blogging as a tool for traditional businesses that sell traditional products and services. The people who manage these companies are going to have to cover a lot of ground to get from content blockers that don't let you visit ESPN to employees blogging on the clock. Not to mention all the corporate policies about what is and isn't fair game for blogging about that would have to be written and enforced. And then there are all the labor and lawyer problems that would arise if an employee got disciplined or fired for unacceptable content, etc.

In sum, most businesses don't trust their employees enough to allow them to blog.

Replace "blog" in that last sentence with just about anything. It goes double (or triple, or pick your multiplier) if your company is unionized - the fact that you need a union is illustration enough that there's a lack of trust.

Is this a killer? I doubt it, at least in the short/medium term. Apple apparently bans employee blogging, and they're doing quite well. Over the longer haul, I think firms that trust their employees will do better than the ones that don't - but it will likely require a new generation of management before we see that.