Using Social Networks

BusinessGreen published a post on social network marketing today. Only yesterday, I received an invitation to join "Earth Hour" on Facebook - a WWF event, encouraging people to switch off their lights at 8pm on Earth Day. Invites are generated by and passed on through friends - thus immediately ensuring some connection/relevance to the reader. It's certainly more effective than one of those hugely irritating facebook ads (just look at the backlash against Experian), which have effectively become spam 2.0. However, I've now joined up for Earth Hour, along with over 400,000 other people ,so they must be doing something right...