The theory behind free Q&A sites is appealing: ask a question to the masses and someone out there should have the answer. Yet, I'm beginning to think that free advice really isn't so great. Here's why:
Yahoo Answers. Probably the oldest and most known of these sites, the quality of answers on this site is appalling. Maybe worse is the quality of the questions. Perusing the questions can be mildly amusing for a while, e.g., Q: "Can your baby get pregnant if you have sex while pregnant?" A: "The baby can get pregnant only if it's a female. If you suspect that your baby is pregnant, try not to have sex again. You run the risk of getting your baby's baby pregnant and that can lead to complications like an infinite loop." But actually, it's overall more just depressing. I can't imagine the site making a comeback; the people contributing seem to be so useless and the domain of answers is so vast, that smart, new participants can't possibly feel any karma by helping others as the probability that they will be helped themselves is so low.
Hunch. I've written about its weaknesses before, but in a nutshell, the challenge is that the value of the site is entirely driven by the participation of the community. Since Hunch allows you to ask questions about anything, my experience is that across the board, the Q&A engine is weak.
Aardvark. I participate in this community and answer a lot of questions (which I like to think add value), but I must admit that I have never had a question of my own satisfactorily answered on this site. Recent example: Q: "What is a good website to discover apartments for rent in Washington, DC (anything but Craigslist please)" A1: "Craigslist" A2: "Craigslist". Their model makes a lot of sense though: identify what you areas you actually know something about (e.g., cooking blogs, the south of France, decoupage) and questions will be filtered before they arrive in your inbox. Both the questioner and I are better off by not waiting on me to give an answer on something say, sports-related.
Mahalo. It's like a slightly more intellectual Yahoo Answers. They try to encourage the karma factor by awarding "points" for participation, and allowing questioners to give "tips" for good answers, but these points only buy you karate-inspired levels. To attain a black belt, for example, you need 13,000 points. Almost all activity, however is in ONE point increments (with the notable exceptions of 1) initially joining and 2) embedding the Mahalo widget on your website, each which is a one time 50 point add), so this is a ridiculous amount of dedication. I'd rather go after a real karate belt.
What would I like to see? A movement towards niche, small community Q&A sites. By definition, all crowdsourced sites depend on their community for their power and in turn, communities are most engaged when they are focused. I like the attitude of Aardvark, but it is still challenged by how diverse it seeks to be; I am getting discouraged by the number of questions I am asked that I am forced to pass on because I have nothing of value to add. Etsy forums is a good example of a dedicated community question site, but it's not quite at the level of a true decision engine.