How do college admissions officers know the authenticity and validity of these "digital" portfolios. How do I know who the work is from?
The portfolios I am describing are actually the product of four years of the student's classroom and coursework engagement with social media integrated across the high school curriculum.
In other words, the portfolio would consist of the student's four-year blog -- which among other things would include blog post editions of all graded writing and daily work in all disciplines -- as well as the student's social bookmarks, videos and other multi-media, and a variety of participatory media projects that would demonstrate creativity, task determination, and intellectual aptitude in ways that SATs and exam scores just can't.
The validity of the portfolio can easily be weighed up against four years worth of work. In other words, the portfolio would not represent some sort of 'capstone' project, but rather would be an honest reflection of four years of formative development.
Because the majority of the work represented by this portfolio will have been completed within the context of classwork and learning and because the tools used in creating the portfolio are authentic Web 2.0 public tools, there is little threat to the 'rigging' of the portfolio by the student -- time stamps, cross-Web intertextuality, and just plain ongoing teacher assessment of the student's involvement in the daily creation and documentation of a learning portfolio contribute to the authenticity.
I'm not talking about students submitting their MySpace pages to college admissions. I'm talking about students submitting portfolios which demonstrate readiness for college by representing four years of the full application of integrated social media tools in the day-to-day coursework of the student.