Portfolios as Valid Assessment Tools

I think portfolios are fairly valid assessment tools, but should not be the only assessment tool used. I see it as more of a preliminary stage, like a resume is used as a preliminary for an interview. Still, I think it's also possible for a wonderful teacher to have a portfolio that is somewhat lacking. Sometimes people aren't good at putting their ideas on paper in a way that sounds professional, and I think that's a big part of a portfolio. Also, sometimes an advantage for a portfolio could be your familiarity with technology, which would make yours appear better, when it reality it is not. So yes, I do believe it can be a valid assessment tool, but I also believe that it's very possible for good teachers to have bad portfolios, though I would say that is probably a rare situation.