Celebrities have a strong influence on people and I'd expect them to use that for political purposes. This will have a bigger influence in an accessible Interactive Democratic system than it does today, because the public will be able to cast their vote on almost any issue.
You may deplore shallow thinking on important issues, but this doesn't need to dominate the debate. In fact shallowness isn't always correlated with celebrity as evidenced by the contributions from Sir Bob Geldorf and many others. I suspect that, though Pop Personalities may have a better than average grasp of the current zeitgeist, there influence may be stronger in creating debates on popular issues than on settling them.