I am not sure why companies -- and some PR agencies -- keep trying to sidestep transparency on the Internet.
You can fake it for a while, pretend that nobody will find out it is really you cleaning up your Wikipedia entry, or intervening in social networks, or commenting on a post. But you leave technology tracks, and you will be outed. And when you are found out, the mistake compounds exponentially. As the title of a post from futurelab says, "PR Disasters Lurk in Web 2.0 Chicanery".
How do you avoid being reputationally jammed? Be honest; be transparent; be open about who you are and why you are intervening.