Over the summer I wrote about the four keys to Facebook page marketing: authenticity, consistency, regularity and engagement. Particularly for those in the e-commerce space... and for those trying to tackle "social shopping"... there is a fifth: exclusivity.

I am not sure that 'exclusivity' is the best word, but the point is twofold:

1. Why should I become a fan? as you think about 'acquiring' fans - what is the incentive? 2. How do you drive engagement?

Exclusivity is the key to both. Portfolio company ShoeDazzle is terrific at this: their 500,000+ Facebook fans get special insights, contests, and behind the scenes access.

I was reminded of this by an email from Rue La La today... who are selling exclusive products today only to Facebook fans: