After Google's recent announcement about +1 recommendations and WOM (word of mouth), it's social networks turn to tell marketers about the growing importance of WOM.
http://www.retailwire.com/news-article/17099/most-brand-conversations-happen-offline-but-social-w-o-m-is-rising
Timing is very important with WOM, seeing customer patterns and following up with every single customer is the key to effective WOM, because we can't tell from the outset which customer will promote your brand or business (and which one won't).
Is WOM part of your online strategy?