People like relearning old lessons again and again, it seems. The phrase "content is king" has been bandied about for many years now, but some people still get confused when a new medium of communication comes along.
What you say is the most important thing in communications. Exciting and powerful media like social networks only work when the content is exciting and powerful. No one will follow your Twitter posts if you aren't interesting, compelling and engaging. Marc Hausman talks about the "entertaining of PR" and he's right. Public relations professionals will only be successful if they develop and distribute valuable and, yes, entertaining content.
The point of this post is remind anyone thinking about integrating a social media component into their communications strategy that what you say is the critical ingredient to a successful campaign. The fundamentals of good PR remain in place. When building and engaging social networks, it is very important to invest in those relationships by bringing valuable content to the discussion. Merely "being present" is not enough.
Nick O'Neil has a good post about Twitter etiquette which, I think, backs this up. Following people on Twitter just so you can notify them when your press release went out is missing the point. Spending the time to engage with people in an interesting, compelling and entertaining way will grow the credibility you are seeking and will build a valuable communications channel.