Search marketing is such a dynamic field because it deals with the full customer recruitment cycle from advertising to converting visits into sales. As a result, search marketing combines both marketing (segment) and human computer interaction (usability persona) views of the customer. In search marketing, a persona is a personification of a class of people with the same purchase intent and who are going to use your website in the same way.
It's basically a way of trying to understand your web customers as people who are going through a selling process on your website and empathizing with the task they face so that you can improve it, making it easier for them to buy. As you might imagine, one of my search marketing students faced with such a task might find it daunting. There's a lot to put together.
I'm happy to report that our student groups are starting to get it though. Here's a presentation by the group working on Liberty at Home, an organization that provides services to senior citizens:
I particularly liked how they summarized the person in one slide with a name, photo, web behavior, and ways to measure success in getting her to buy. They'll need to continue to refine and verify this persona by talking with their non-profit and looking at the data, but it's a good start.
The group working with Dance Marathon at University of Michigan also made a good start at a detailed persona. You can see their work here. I would have liked more refinement on how to measure sales success with this persona, but I think they nailed the concerns a person responding to this site's campaign on autism might have.