From "Socialized Media" by Tim Manners at Fast Company. Manners gives excellent examples of what's not working and what might. I think two key points he makes are valuable to any marketer - 1. listen and 2. add value. You cannot go wrong by doing those two things. I encourage you to read the whole article.
As one respondent put it: "If you sell (unless you are a very cool web app), you lose. Don't sell. As a marketer: network. Help people. Advise. Create value and add to the conversation."
Nobody has really figured out how to do that yet. But it's worth considering the possibility that smart marketers won't even attempt to be part of the conversation, much less interrupt it. It could be that the real marketing potential of online social networks is listening, not talking.
The point is, if we're not helping people live better lives, we are not helping ourselves. If all we are doing is interrupting people who don't have time for interruptions, we can't expect their attention. If all we are doing is annoying people who have zero tolerance for annoyance, we can't earn their trust.
If all we are doing is pelting people with endlessly irrelevant messages, we can't claim their loyalty. And if we can't claim their loyalty, we don't have a prayer of a positive return-on-investment.
We can run whatever media-mix model we like, but all we're likely to achieve is a marginal improvement on what is otherwise an unmistakable downward spiral of failure.