This short sentence has a powerful message, with a straight reasoning. I do not know, since when parts of our movement started to use it, but it is commonly used right now. The last time I read it was by Joshua Blakeny here http://www.rabble.ca/blogs/bloggers/campus-quotes/2011/02/has-national-post-declared-fatwa-911-studies (sorry "student" ;-), no offense)
Other researchers did use it as well.

But: Did Einstein said this? In wanted to know when and where he made it. I searched Wikiqoutes for it, but found nothing.
Only a similar statement, under missattributed:

March 2, 2010, 11:00 PM ET

Details of “Einstein” Cyber Shield Disclosed by White House

The Obama administration lifted the veil Tuesday on a highly-secretive set of policies to defend the U.S. from cyber attacks.

It was an open secret that the National Security Agency was bolstering a Homeland Security program to detect and respond to cyber attacks on government systems, but a summary of that program declassified Tuesday provides more details of NSA’s role in a Homeland program known as Einstein.

The current version of the program is widely seen as providing meager protection against attack, but a new version being built will be more robust–largely because it’s rooted in NSA technology. The program is designed to look for indicators of cyber attacks by digging into all Internet communications, including the contents of emails, according to the declassified summary.