Viral Expansion Loops.  Defined the success of Hotmail, Google, Craigslist, Ebay, Amazon.com, Paypal, LinkedIn, Flickr, the list goes on.  They all incorporate “virality” into the functionality of their core existence.  Viral Expansion Loops are consided the type of engineering alchemy that with executed properly, they are self replicating.  No wonder Web 2.0 seems to be the formula for success.  The likes of Myspace and Facebook were designed specifically to exploit the notion of viral loops; driven by user generated activity that drove consumer adoption into the stratosphere.  Viral expansion loops have long existed offline too…think Tupperware parties, multilevel marketing, chain letters, and even pyramid schemes.  The newest app to catch the viral loop craze – Widgets.  Now we are moving beyond viral loops to viral networks and double viral loops.  Is your brand capitalizing on viral expansion loops?