Thumb, a mobile app that allows users to ask questions like “Does this make me look fat?” or “Do you love cats that cuddle?” (a genuine question posed by a user, believe it or not), is spreading like wildfire. Some 1 billion responses to around 20 million questions pass through its mobile app on a yearly basis, and the company has doubled its sign-up rate in the last three months. The company is announcing today that it has added a new “Election 2012″ question category, and is planning to test location-based filtering with a small subset of users.

Launched in 2010, Thumb is a fairly simple service. Users upload a picture of whatever they would like to get a response on and then ask the masses to cast their votes via a “thumbs-up” or “thumbs-down.” Questions can be placed into a specific category, such as “Food & Drink,” “Places & Travel,” or “Relationships,” and responses can be further narrowed down  based on age group, gender, or your Thumb friends and the contacts on your phone.

Thumb CEO Dan Kurani says that the company plans to introduce location-based specifications to a small number of users – around 10,000 – in the next week or so.

The specificity of these location-based preferences remains to be determined. In the beginning it will be limited to the user’s current location, but Kurani says that in the future users may be able to ask a question of a specific location. In other words, if I wanted to know where the best pizza in San Francisco is, then, I’d be able to ask San Franciscans instead of users from who-knows-where.

By adding location-based functionalities, Thumb will be sitting on that wonderful, buzzword-y “SoLoMo” (social, local, and mobile) trifecta. But Kurani says that the company wants to take it slow and get the feature right before rolling it out to as a public feature.

One of the things at stake with limiting questions to a specific location is speed. Within minutes of posting a test question I had over 50 responses, which the company says is par for the course. A fair number – around 25 percent, again mimicking the service’s average – of these responses included text comments that elaborated on the otherwise binary input, offering context and depth where a user felt appropriate.

This speed is a key differentiator between Thumb and another question-and-response service, such as Quora, which may not populate as quickly. I would still turn to Quora for more in-depth questions or questions for a specific person or audience, but if time is of the essence (“Should I buy this?”) Thumb would be my, and 1 million other users’, first choice.

[Image courtesy Wikimedia]