By now, you've surely heard of the second-largest acquisition in tech history, with Facebook acquiring WhatsApp for $19 billion.

However, you may be less familiar with other messaging apps like LINE, KakaoTalk, KIK, Nimbuzz, SnapChat, Vibes, Whisper, and many others.

If you think messaging apps are just a free way to communicate, you’re missing their potential: They are Mobile’s Trojan horse, as explained by my colleague Julie Ask here.

Messaging apps are mushrooming.They illustrate perfectly the age of the customer, which Forrester defines as a new business era where your customers are now empowered through social, mobile, and other technologies giving them the power to disrupt your business. Why? Because they are mastering the four key market imperatives Forrester has identified as critical to differentiate in the age of the customer:

■  Transforming the customer experience over SMS and other messaging tools. Messaging apps offer differentiated and seamless experiences over SMS and other mobile communication tools. For example, they offer advanced group messaging functionalities, multimedia features, constant innovation, and ability to opt-in or follow brands at consumers’ convenience. They are now morphing into marketing platforms redefining social media.

■  Becoming digital disruptors. Most of these apps were created back in 2010 and 2011, tapping into digital platforms like iOS and Android ecosystems. They benefited from their ability to connect directly to huge audiences and to leverage existing cheap and open infrastructure tools. There's no doubt that messaging apps have quickly disrupted the good old and lucrative SMS business, led by telecom operators and pioneers like BlackBerry Messenger, that did not distribute its app early enough on other platforms.

■  Turning big data into business insights. Anonymous apps put aside, messaging apps know a lot about their customers (profiles of customers, how much time they spent on the app, who they interact with, mobile behaviors, etc.). For now, most messaging apps have used advanced analytics to improve their own experiences, but they could offer tremendous value as new listening platforms for marketers.

■  Embracing the mobile mind shift. Last but not least, most of these new apps are mobile-centric offerings designed with a mobile-first approach from scratch to meet more demanding customer expectations.

I am working on a new report on messaging apps and what they mean for marketers and will share a preview of this new research tomorrow in my speech, "Delivering Real-Time Value On Mobile And Social," at Forrester's Forum For Marketing Leaders in London (May 13-14).