When it comes to online communication, the big thing these days is mobile messaging.
For proof of that, you need look no further than Facebook's $19 billion purchase last month of popular messaging application maker WhatsApp. But WhatsApp is only one of a handful of mobile messaging services that have been gaining attention lately for providing consumers with a new way to communicate.
"They're the cool thing of the moment," said Danielle Levitas, a mobile technology analyst with IDC.
The new services, which include WeChat, Line, Viber and Telegram, were built from the ground up as mobile apps. They were designed to allow users to swap messages across their mobile phones while avoiding pricey texting fees.
Many have caught on rapidly, particularly in developing countries where texting prices can be particularly high. WhatsApp, for example, has some 450 million active monthly users and a million more users register with the service each day. It and many of its rivals are benefiting from so-called network effects; that is, the more people who join them, the more likely it is that those users will draw in others.
Generally free to download, the new messaging apps tend to charge small fees for particular items or services. WhatsApp charges users a $1 yearly subscription fee after the first year of use. WeChat and other services charge from $1 to $3 for custom background themes and other add-ons.
The new messaging apps offer advantages over older messaging services, such as AOL's AIM and Skype. One feature common to many of the new apps is that users log into them using their mobile phone numbers. The services also generally encourage users to use their real names when signing up.
That makes it easier to find friends than when using instant messaging services, which generally required users to create unique log-in nicknames. In order to find your friends on them, you had to know their nicknames, which could often be obscure.
The new services work a lot like iMessage, Apple's messaging service, which allows iPhone and iPad users to send each other messages without incurring SMS charges. But unlike iMessage, services like WhatsApp and WeChat allow users of devices from different manufacturers to exchange messages. WhatsApp, for example, has apps for Android, Symbian, BlackBerry, Windows Phone and iPhone as well as Nokia S40 feature phones, and users can send messages from one device to another.
Another cool feature of many of the new services is that they make it easy to send group messages. Users can blast one message to a group of friends, or carry on long-running conversations with several other users. Some apps, such as WeChat, will generate custom QR codes, which are like square bar codes, that users can scan to join a particular chat group.
The group messaging feature is what got Owen Remeika hooked on WhatsApp. For Remeika, a 25-year-old San Francisco resident, WhatsApp has replaced email and text messaging as a way to keep in touch with his college buddies.
"I've stuck with WhatsApp, because so many of my friends are on it," he said. "It makes it easy to contact all of them."
Some of the apps also allow users to personalize the apps with particular background themes. In Line, for example, users can buy Mickey Mouse or Hello Kitty themes. And many offer "stickers," which are similar to emoji. They're special drawings, frequently animated, that can be sent in place of text to express thoughts or emotions.
The new apps do have some shortcomings. Unlike iMessage and older PC-based messaging apps, many don't work well or at all on tablets such as the iPad. And some of the services, including WhatsApp and Kik, don't offer PC apps. So while you can chat with your friends when they are on their mobile phones, you can't necessarily reach them on their computers.
What's more, unlike many of the older instant messaging services, none of the new ones talk with one another and they generally don't allow users to connect to them using third-party applications. They also typically don't send messages over the SMS network to folks who haven't signed up yet. So, depending on what services your friends are on, you may find yourself having to run multiple messaging apps to reach them.
Many of the new services are popular only in particular countries. Most of the WeChat users, for example, are in China, while most of KakaoTalk's are in South Korea. Unlike SMS, none of them are widely used worldwide.
And some of the services offer fewer features than the older messaging applications. Unlike Skype or even Yahoo Messenger, for example, WhatsApp and KakaoTalk can't be used to make video calls.
If the past is any indication, today's popular messaging services will be yesterday's news in a few years. Facebook's purchase of WhatsApp brings to mind Microsoft's acquisition of Skype three years ago, when it spent billions of dollars for Skype's millions of users.
With Facebook's acquisition of WhatsApp, mobile messaging apps have come into their own.
-What they are: Apps that allow users to send text messages, photos, videos and sometimes make voice and video calls from one mobile phone to another.
-Popular messaging apps: WhatsApp, WeChat, Line, KakaoTalk, Kik, Viber, Telegram
-Cost: Generally free to download and use. WhatsApp charges users $1 a year after the first year. Other services charge for add-on features.
-Advantages: Allow users to send text messages without incurring SMS charges; let users send messages or make calls across different phones, and connect with friends without having to know or use obscure user names.
-Disadvantages: Some don't offer programs for PCs; many are popular only in particular countries; none of the programs interconnect.
Explore further: Groups seek privacy review of Facebook-WhatsApp tie-up