It’s time for Silicon Valley to ask: Is it worth it?

Infinitely. And I don't get the outrage that foreigners have that the American people aren't outraged that we are spying on foreigners. That's what spies do - for both sides. The electronic monitoring of foreign communications is the charter of the NSA. By the way, China is quite silent on all of this because they are hacking the shit out of the US trying to steal everything from political to military to commercial secrets.

The outrage about the NSA is domestic spying. Intercepting communications of Americans outside of the US is a gray area but doing it to Americans on US soil is completely against the NSAs charter, tramples due process, and takes a dump on the Constitution. Anyone who said that was ok needs to be thrown into prison.

The wider implications are earlier in the article. Wearable recording devices and biometric security devices shared in the cloud? Probably better to assume the government will compromise them if it wants to, and might well do anyway, just in case, with or without the blessing of Silicon Valley. That's something to take into account when deciding if you actually want them. It's not an entirely new phenomenon though; the same was true of brick-sized mobile phones a couple of decades back.[1]

Your chances of having your life seriously affected by PRISM may or may not be higher than your chances of having your life seriously affected by terrorism [2] but it's a stone cold certainty that public criticism isn't putting the spooks to bed. Intelligence agencies have never really depended on being in tune with public sentiment or in line with the law.

[1]There's a well-publicised trial going on at the moment in the UK over "phone hacking" in the 1990s, where the organizations snooping on people's voicemails were newspapers. In a beautifully ironic touch, one of the major revelations of the trial so far is that two of the media moguls in question were having an affair. They were incriminated by a Word document; a love letter that may never even have been sent, and certainly wouldn't have come to light if they hadn't had to hand over their computers to prosecutors.

[2]both are higher than the article's "1 in 20 million", but not high enough to be likely if you're not a major public figure

It could just be a challenge for them. Where else can you not only get away with, but be rewarded with a good salary and a pension for hacking into the most secure systems on earth? It must be thrilling to be 'Competing' against the best security engineers, best practices, with a massive budget to support your activities.

It could be that with their security clearances, they know things about threats that make their decision to work for the NSA a moral imperative. It's entirely possible that there are some really horrific classified things that were stopped via similar spying activities, so intercepting some Gmail messages seems like a much less evil alternative.

They could just be 'blindly' patriotic, have faith that the faults of the government are outweighed by the need to keep the US on top of the world.

There are many possible reasons.