There is a divide between the scientific community about involvement in popular science. I would define it as involvement in NatGeo/Discovery type documentaries, writing columns for newspapers/magazines, blogging about articles of popular nature (Like End of the World, Tsunami or whatever).
Does involvement in such issues harm one's reputation in academia?
I have frequently seen grad students shy away from such opportunities because they think they will be made fun of or won't be taken seriously when they go and speak about "actual" research.
(Although I am talking about grad students, the scenario isn't very different for faculty as well IMO)
Some people like Stephen Hawking or Richard Wiseman have actually authored best selling books. Whereas a majority of people in academia stay in the confines of the journals.
There is a field in which academics are paid to find "the Equation for the perfect X" so that the company that makes X can write a news story about it. I am not sure how academics generally feel about this, but it certainly gives off sellout vibes. On the other hand, if Stephen Hawking is allowed to do it then maybe it's OK?