Many Q&A websites seem to have come and gone. Yahoo Answers has been around since 2005 (a year before Blurtit) and is still around today.
Sites like Formspring launched years later. In the case of Formspring, it started in 2009, but was rebranded as Spring.me and became more about socially connecting with people.
Answers.com, Ask.com... There quite a few Q&A sites still around today.
Two of my favorites (other than Blurtit of course) are Quora and StackOverflow. They're a little more geared towards the "startup" and "tech" world, but both are very useful in my day to day browsing.
What Q&A sites do you use? What do you think makes a good Q&A website?
