You can be compelled by the US government to do things you might not like to do. Google can either comply since they are a US based company, or not. The benefits of compliance outweigh the downsides of not complying.

>secret unethical, most likely unlawful and surely unconstitutional request?

There has been no evidence that what the NSA is doing is illegal. It has congressional oversight and approval.

I'm thinking that the US Government would have a much harder time prosecuting a high-profile, wealthy CEO over a systems administrator no one had heard of until a month ago. And the media attention would be harder to derail.

  I'm thinking that the US Government would have a much 
  harder time prosecuting a high-profile, wealthy CEO 

  "Only One Big Telecom CEO Refused To Cave To The NSA ... 
   And He's Been In Jail For 4 Years

  We know what happened in the case of QWest before 9/11. 
  They contacted the CEO/Chairman asking to wiretap all the 
  customers.  After he consulted with Legal, he refused.  As 
  a result, NSA canceled a bunch of unrelated billion dollar 
  contracts that QWest was the top bidder for.  And then the 
  DoJ targeted him and prosecuted him and put him in prison 
  for insider trading -- on the theory that he knew of
  anticipated income from secret programs that QWest was 
  planning for the government, while the public didn't 
  because it was classified and he couldn't legally tell 
  them, and then he bought or sold QWest stock
  knowing those things.

  This CEO's name is Joseph P. Nacchio and TODAY he's still 
  serving a trumped-up 6-year federal prison sentence today 
  for quietly refusing an NSA demand to massively wiretap 
  his customers.

He would go to jail. And then, instead of being a powerful executive in a strong position to push the government to do the right thing, he would be powerless.