In short, the bikeshed problem:
If you go before the Board of Directors and ask for 1.5 billion dollars to build a nuclear reactor, no one will review or discuss the details of the plant. They will assume that experts have been over every inch of the plans, and not want to look foolish by asking a silly question.
However, if you ask the same group to approve a 30 dollar expenditure for lumber with which to build a bikeshed (presumably a British term for the smallest possible building) then be prepared for a 45 minute discussion about all aspects of the bikeshed, including the color of the paint. The explanation for this is that everyone can grasp the scale of a bikeshed.
To transform this problem to Stack Overflow terms, questions that are trivial such as "How to convert a C string to a QString or "What is the difference between . and ->" get a lot more views, answers and votes than real questions of the form "How do I frob this widget" that bother real professionals. Fewer views mean less possible votes for good answers and hence less incentive for people to answer.
How can Stack Overflow solve this problem?