The result of:
(num_person-hours_saved_by_SO * num_of_developers_in_world * dev_hourly_rate)
must be staggering. I'm sure companies around the world can point to SO for a non-trivial percentage of bottom line revenue.
And forget about the bean counters for a sec: as a DEV, SO saves so much pain that I have no idea what I did before it came to be.
SO is truly doing God's work (and I'm not a religious man).
There's also a negative effect on global developer skillset when developers don't have to dig deeper into things or read documentations because they can just find a working example from SO. Although Stackoverflow still probably has a positive net effect for global skill of developers regardless. But a developer who learns from the bottom up will most likely outperform a developer who relies on finding working solutions from SO in the long run. And while a company prefers to have a solution right now for monetary reasons, the quality of developers the global workforce has in the same long run dwindles when the primary goal is to save developer hours "right now". Again highlighting that I still do consider SO a net positive, just that it is not a flat out black and white hours saved function
I consider “being able to resourcefully look up the answer to your question” a critical developer skill, regardless of whether that answer comes from an online forum or page 254 of the official spec or finding the right academic paper. Having a nice searchable online resource contributes positively to this developer skill!
That said, SO is still a wealth of information.