Another buzzword for the Communications world, created in 2006 by Rohit Bhargava His original five rules for conducting Social Media Optimization are:
1. Increase your linkability
2. Make tagging and bookmarking easy
3. Reward inbound links
4. Help your content travel
5. Encourage the mashup
Another source with a longer list is The NewPR Wiki
Definitely not a term to be ignored in the new Communications world.