Big Agencies & Digital Life: Something Runs Afoul

Having spent the majority of my life client side, I'm likely not an aficianado on big agency culture. What I have seen in more than a few marbled hallways is a troubling mix of fiefdoms, ego  challenges, a shallow understanding of what makes them look good to a client and an all-too-familiar understanding
of what makes them look good to their industry peers.

In the same breath, some of the more brilliant  and genuinely interesting and passionate people in the communications industry are floating, or more likely ranting, at different levels within agency land.

Recently, I have seen at least 4 digiterati who I like and respect and by all accounts, are exceptionally good at what they do, leave big agencies in Toronto.  Although all have taken the high road and have either been quiet or complementary of their former firms - I find it more than coincidence these gaping online talent holes exist at the exact same time the Critical Mass, Rare Methods, Blast Radius and Organics of the world thrive.   

What's wrong here?:
Do big agencies not understand digital culture?
Are broadcast creative teams still TV first, fight for the crumbs everybody else?
Have clients given up on big agencies ability to delivery solid digital work?
Is the efficiency required by big agency models reducing "outside the box" online innovation?
Are older presidents/CEOs not familiar or comfortable enough with the fast-moving digital worlds to affect real change?   
Are media dinosaurs reinforcing a "paint by numbers' approach to digital campaigns?
Does it come down to big agencies can be good at only one thing and one thing only, usually broadcast creative?
Is "integration" paradoxically better executed across agencies then within an agency (I would wager in that 80% of firms, digital staff don't sit close to their traditional peers?
Is online being seen as strictly a media tactic vs. a true business enabler?
Is Canadian branch plant mentality to online communications handcuffing and frustrating brilliant digital creative?

Hmmmm. all I know is something smells fishy here. Any thoughts from the e-rafters?