Venerable educational institutions like Harvard and MIT are giving away education online for free in a new partnership called Ed X. Classes start in the fall -- online. Students do five to 10 minute videos, interlaced with online exercises that give instant feedback. There's no emails -- it's all browser-based and online. And at the end, if you master a subject, you get a Certificate of Mastery. Which is neat but not quite a Ph.D or anything anyone's ever heard of. So what good is it?