Over the past one and a half years, Stack Overflow has lost around 50% of its traffic. This decline is similarly reflected in site usage, with approximately a 50% decrease in the number of questions and answers, as well as the number of votes these posts receive.
The charts below show the usage represented by a moving average of 49 days.
What happened?
Half of a fuck-ton is still a lot. If they scale down their operational costs they can still run a very comfortable business for a long while on these kinds of numbers.
I think the point is not their viability as a business but their relevance in the industry.