Quite a while ago, I had a fairly bad experience at Stack Overflow and wrote a blog post about it:
StackOverflow Impressions - Too Many Rough Edges
I have now returned to being a contributor at Stack Overflow. But why?
More and more Google searches are leading me to Stack Overflow for answers. The answers are often useful. Stack Overflow has no meaningful direct competition.
I'm a pragmatic person and I appreciate that the service provided by Stack Overflow is useful.
Since I'm gaining value from the site on a regular basis now, it makes sense to try to help out and "give back" to the community by providing answers when possible.
Stack Overflow is "good enough" to support.
Also, while I believe the benefits of putting a Stack Overflow reputation number on a resume are overstated (and include some small amount of risk), I do think asking and answering questions on Stack Overflow is an important indirect marketing opportunity for individuals. As one example, if a blog post I've written answers a question some one asked, answering the question on Stack Overflow with a pointer to my blog post is helpful and increases the useful life/value of that blog post. I think blog posts are a great way to expand the programmer knowledge base, but not all blog posts will be easily found through Google searches (Providing links to your blog from Stack Overflow will not increase your blog's page rank, but people will click through none the less).