Not sure why should be considered a problem. StackOverflow offers reviewed, edited documentation from people who actually use/enjoy to technologies they're describing.
By providing documentation filtered through the real world, you get useful information that describes how features DO work, and not how they WOULD work if they were implemented the way some unknown documentation writer described them.
To me, the SO solution is MUCH better than written documentation, and I've quickly picked up a working knowledge of entire new platforms, languages, etc. just by getting the answers to questions I needed, rather then sifting through tomes of irrelevant information and "Hello World" examples. SO is good documentation; perhaps companies should have their doc writers participate in discussions there, rather than formatting new whitepapers and PDFs.