Jared Spool discusses the dangers involved in creating personas with little or no user engagement. There comes a point where the persona creation exercise is simply a process of creative writing and therefore virtually useless.
As someone who is a firm believer in the value of personas even when limited research data is involved, I found this a thought-provoking read.
I suppose I've been of this view as I work so often with people who deal first hand with target audiences almost daily. I've seen personas - even without formal research data - as a way to harness years of experience and to give these colleagues a voice in the website development process.
But if the people creating the personas don't have any first hand experience of the target audience to draw on, then it's a different matter...
When Does A Persona Stop Being A Persona? - blog post by Jared Spool