LIVE FROM GSMA MOBILE WORLD CONGRESS 2012: Messaging apps company WhatsApp has seen its users sending more than 2 billion messages per day, Jan Koum, the company’s CEO, told Congress today.

“It’s been a really humbling experience to witness that, and to understand that so many people are relying on something we built,” he said. The company passed the 1 billion mark in October 2011.

Koum described the core features of WhatsApp as “basic messaging, group chat and media sharing.” However, usability is also a key consideration, with the executive noting that “we also worked hard to make sure that it’s really simple, and worked hard to make sure that the application is always working correctly.”

Cross-platform support has been a key part of WhatsApp success, with Koum noting that it currently supports six platforms. He said that the company has “worked really hard” to enable this – “if you have iPhone, or BlackBerry, or Android, or Nokia, or Windows Phone, you can message with your friends.”

Although the app is now seeing some considerable success, it was not until it was evolved from its basic premise – to send status updates to contacts – that it became a success. Discussing the original incarnation, Koum said: “we built it, we really loved it, we got no traction whatsoever.”

After moving toward a more traditional messaging proposition, “overnight, we saw just huge, huge uptake and user response – it was great.”

Koum said that the reasoning behind its adoption of a subscription business model was two-fold: user experience – “people don’t wake up every morning and say they want to see more advertising” – and to avoid the need to amass subscriber information.  “We don’t really want to collect any data about our users,” he said.

The potential of partnerships with operators was also mooted. “We would like to work them, and we’re looking to leverage a lot of the billing capabilities that operators have today.”