Do you remember when natural language search engines (sometimes called “question engines”) were hot? It was about twelve years ago. Ask Jeeves was all that. Everybody wanted to be able to search in plain English (or Spanish or French or Esperanto or whatever their preference was.) I remember reviewing a search engine called Electric Monk and quite liking it.

But natural language searching went somewhat out of fashion, replaced by the more practical cluster searching, and by Google, which is actually not a bad natural language search engine but which never made a big deal out of it.

Fast forward to 2010, and question engines are hot again, only this time they’re human-powered. I can’t prove this, but I suspect that it’s because people have gotten used to almost real-time interaction in social networks; toss out a question on your Twitter feed and according to the question and your followers, you could get dozens of replies within an hour. Add that to the ongoing presence of deliberately structured sites like Yahoo Answers and the Q&A feature on LinkedIn, and people became blasé about the idea of hundreds (thousands, more) of people hanging around a Web site, ready to answer whatever question you wanted to holler into the void.

In February I reviewed Aardvark (which had been acquired by Google), and now I am hearing about a new Q&A engine called Quora, which is available at http://www.quora.com/. Well, it’s extant at Quora.com, but not yet available; you can leave your e-mail address for an invite.

According to a recent article in TechCrunch, the beta is a hot ticket, so don’t hold your breath. Also according to the article, Quora was founded by ex-Facebook employees and has gotten a recent round of funding. Check out the article for a brief interview with a couple of the founders and one investor.

I think the popularity of Q&A services like this lie at the intersection of real-time searching — how 2001, to post a question on a site and get an answer back in a couple of days! — and researching in a mobile situation, where deep research is generally not necessary but where you might have lots and lots of small questions (“Where can I find parking in Savannah, Georgia?” “Are there any traffic accidents on I-20?” “What happens if I accidentally drive into the ocean?”) It seems to me that successful development will require a good sense of community, the ability to deliver answers a lot of places very quickly, and potentially integration into other social systems where a lot of data is flying around right now — Twitter, maybe, or LinkedIn.

Definitely something to watch.