Jenn Prentice is content manager of technology Q&A site Experts Exchange.

With the rise of Quora, Hipster and other question and answer services, Q&A sites have once more become a hot topic. The resurgence begs the question:  What makes a Q&A service successful? Is it the community? The content? The business model?

If you’ve ever asked a question in a search engine, you’ve probably stumbled upon one of the massive legacy Q&A sites. Yahoo Answers, and other general-purpose Q&A sites have been around forever, providing solutions with varying degrees of effectiveness. The content is often (though not always) shallow, leaving users wanting more.

Recently, Quora’s “continually improving collection of questions and answers” has seemed to position the Silicon Valley darling as the Q&A leader, but I don’t think we’ll see one Q&A site dominating the market.

Rather than a category killer brand in the Q&A space, perhaps the emergent leaders—yes, I do think there will be more than one–will be the websites that can create a customizable platform to meet the needs of niche communities.

Here’s a roundup of a new class of Q&A websites and the unique characteristics and innovative ideas that could help them succeed:Quora & Aardvark: Real-Name Knowledge
If you’re looking for a quick and dirty response to your question about the best TexMex joints in San Antonio, Quora may not be the venue for you; but that is partially where its strength lies. The collaboratively edited site aims to provide people with the definitive answer on thought-provoking subjects and allows the folks answering the questions to wax eloquent on the topics they are most passionate about.In addition, people answering questions on Quora are encouraged to use their real names; and you’ll find a number of industry heavy-weights chiming in on questions related to their area of expertise.  Want to know the best launch strategy for a web startup? Robert Scoble has the answer. Interested in how Etsy solved the chicken and the egg problem? David Lifson, former head of the Etsy product team, will tell you.As having a solid online reputation becomes more important to both search engine ranking and prospective employers, Quora’s real-name authoring could be the boon its business needs. Right now, Quora’s most famous knowledge sharers are those in the tech industry.  But if the site can draw in big names from other industries while helping the rest of us position ourselves as an authority in our field, it could easily become the definitive information repository for knowledge workers.

Speaking of real-names, Google’s Q&A property, Aardvark, leverages the people you know in real-life to answer your questions. And therein lies the benefit and drawback of the service. Aardvark links up with your Facebook and/or Gmail contacts, making the answer you receive only as good as the collective knowledge of your friends and contacts. Then again, if you trust your friends implicitly or run in an uber-intelligent circle, Aardvark could be your preferred Q&A platform. Simply type a question into the self-proclaimed social search engine and you should receive an answer in 10 minutes or less, provided someone in your network is online; and since you can ask a question via the web, instant messenger, email, Twitter or your iPhone (one of the better features the site has to offer), there’s a good chance someone is.

Still, the question of why people should sync Aardvark up with their Facebook profile, rather than just pose a question in their Facebook status is one that Aardvark itself would do well to answer. Additionally, last week’s launch of Google+ has interesting implications for social Q&A, but it remains to be seen if Google will choose to leverage Aardvark as its Q&A platform or leave it wandering in the wilderness.

LOCQL & Hipster: Getting Local with It
Since they just come onto the Q&A scene in the past few months, it’s too early to tell how location-based Q&A services LOCQL and Hipster will fare. Both promise information you cannot find elsewhere about places and things to do in your area, and LOCQL (which is currently available for use, while Hipster is not yet ready for public consumption) leverages “the people who know you best” (for example, those in your social networks) to help you find the answer to your question. While both sites have a mountain to climb to win over Yelp and Foursquare users, one or both Q&A sites can attract a solid following by providing an easy-to-use interface that lets people share and consume location-based information, anytime, anywhere. If LOCQL or Hipster merges with Yelp or Foursquare, they’ll be dominating search rankings one city at a time.

Stack Exchange & Experts Exchange: Always on Topic
Having been around since 1996, Experts Exchange (the company I work for) provides users with over 3 million technology solutions in nearly 900 different topic areas. Recently, Redsource Interactive, the parent company of Experts Exchange, launched 25 microsites on topics ranging from Excel and SQL Server to KTM motorcycles and classic Ford Broncos. In order to ensure the quality of answers, the person who asks a question on Experts Exchange or one of its microsites has to accept an answer as the solution to their own question. Community members who answer questions on Experts Exchange earn points towards expert certifications and site rankings that indicate how much an expert knows about any given topic.

Stack Exchange started in 2008 as Stack Overflow, a free site for programmers to get help with technical questions, has grown into a network of 55 question and answer sites on topics ranging from gaming to project management to cooking. Once a question has been asked, community members provide answers; and good answers get voted up in the thread, allowing readers to see the best answer right away. In addition, registered Stack Exchange users can earn reputation points when their answer gets voted up, allowing readers to see how much “expertise” they have in certain topics.

Specificity of subject matter is what makes these two sites successful. Still both Experts Exchange and Stack Exchange would do well to remember their core competency (technology Q&A) and continue to devote the most resources to those sites until the content and communities on their newer sites have matured.