I would also add:
"Know your audience".
Who do you want to write for? For example, I have multiple blogs, and have tried to maintain some sort of continuity of 'character' (?...if I can call it that!) between my blogs, yet maintain an awareness of who might be interested in reading what (and how they can find it to read it!).
"Think about your peers".
Should your thoughts/work/articles be accessible in such a way as to be 'peer reviewed'? or do they help to extend an area of research? or simply connect with thoughts and articles of likeminded people just for fun?
"Know your sources".
This is something we constantly remind our students of; so when blogging we should encourage the same practice to combat plagiarism and mediocrity! This way students become discerning information architects and knowledge managers! :o)
These points may be 'secondary' points to Robinson's list, but worth reviewing if you're thinking of using blogs in education especially, or for business purposes.
What do you think of Robinson's list? What of my additions? Any others you can think of?