Question and Answer Services backlinks

Often, users in search of the information they need come to the service of questions and answers. Such services collect good traffic on low-frequency queries, many of which are specific issues.
Often, these services are in the top for such requests. All this makes question and answer services interesting resources for attracting targeted visitors to their site.
The most popular question and answer service now is Yahoo! Answers and Quora. Other popular sites:
AardVark
Able2K
Answer Bank
Answerly
Anybody Out There
AskDeb
askville
Blurt it
Friendfeed
Funadvice
Mahalo Answers
WikiAnswers