Which Network Is Strongest: University or Professional?

This post could have gone under Psychology (why is one Network stronger) or under Web/Tech as well (how each Network is mapped and proved), but it's under Business because that's what I can speak to.  Initial proof, both hard and anecdotal, indicates that ties with people you were tight with at your university bind stronger than ties with former co-workers.  The anecdotal proof is on an individual basis - are you tighter with old classmates or with former co-workers?  The hard evidence is something I'm compiling out of interest in a post last week about the connection between something Mark Cuban said and why it's actually playing out the way he thinks it will.  That spurred me to analyze Google's Board of Directors, mapping each Director's boards served on, former employers, and former universities they attended or had a role in the administration (faculty, President, etc.)  There doesn't seem to be any overlap in boards served, which is an example of solid corporate governance principles (something they picked up by their study/emulation of Berkshire Hathaway's principles, no doubt), nor do I see any cronyism associated with common former employers.  I do see multiple Princetons, multiple UC Berkeleys, multiple Stanfords, and multiple UC SFs on the board, however, which could indicate the presence of strong alumni networks.  Another consideration is the fact that there may be fewer top-notch universities than top-notch companies, but that's another project.
I've just started working on Sun Microsystems, and will then proceed to Apple, Cisco, Amazon.com, Intel, and other Valley icons that have been around a while and look to continue to be around for a while.  I'm an analyst, not a programmer, so I can't produce on my own the desired end-product, which would be a cloud-based network graphic of the interconnectedness of Silicon Valley board members with strong or weak links to other boards, former employers, and educational institutions.  THAT tool would be both fascinating and useful (LinkedIn should produce something like this, if they don't already).