These four companies have a few things in common apart from September being a fabulous month for them - they are all (except Rocket Fuel) subscription-based, are all cloud-based, and they are all based in the bay area.
The other thing they have in common is that they are also all founded by salesforce.com alumni. Ever since the original "Fairchildren" that left Shockley Semiconductor, great companies in the bay area have spun out more and more entrepreneurs ready to start something new, and also generated the financial backing to help them.
From the PayPal mafia which has created some well known companies recently like Telsa and LinkedIn to Oracle, which not only counts Marc Benioff, founder of salesforce.com, but also Thomas Siebel, founder of Siebel Systems, many companies are training grounds for another generation of entrepreneurs. Salesforce.com is no different, where Tien Tzuo led out, founding Zuora in 2007.
Just as Robert Noyce removed the hierarchy at Fairchild, salesforce.com also had great lessons while working there, with Marc Benioff encouraging everybody to "be your own CEO".
I've compiled a list of the startups founded by salesforce.com alumni here - I'm sure I missed some, please leave a comment or email me at leo [at] appme.sh. Some are now dominating their industries, other still starting up:
At PandoDaily, they've begun charting some of the diaspora for other companies:
I don't know what Stephen Few would say about the visualization, but the data is intriguing to explore.
Looking at the long list of companies, it's going to be interesting to see which truly become great and spawn the next generations of companies.