A university library search usability project at Edinburgh has been detailing the steps they went through in the production of their personas. One aspect that particularly caught my eye was the risks around personas getting stale and out of date.
While I'm still of the opinion that any personas are better than no personas - within a group of non-specialists developing a website, anyway - the 'zombie personas' referenced from a presentation by Tom Allison (no relation!) are thought provoking.
Personas in the UX2 project - blog article by Lorraine Paterson