Messaging apps have long been regional due to network effects. In Canada, my friends used MSN Messenger, in the US, AIM. In China, QQ/Wechat, in the US it's mostly been SMS/iMessage or Facebook messages. I've yet to locate a Whatsapp ___location, but I guess Nigeria is one.
Germany, too, as SMS flatrates got to the market rather late and there was some social networking confusion with the VZ group, slowing down the expansion/adoption of Facebook a bit.
Most smartphone users in Singapore use WhatsApp for general texting too.
On the other hand, WeChat, LINE and KakaoTalk seem to have rather limited audiences here. (Much of the LINE usage between myself and friends is sticker spam.)
chrischen: What do iOS and Android users in your circles use for free cross-platform texting?
Here in Japan it's hard to find anyone under 40 who doesn't use Line for nearly all their messages. The carriers make it extremely expensive for people to communicate with users on other networks so people just circumvent texting and calling with line. I've asked my friends why they use it and they all say because they like the stickers.The market was wide open for a while, it just took some good marketing.
For cross platform we just use Facebook message and SMS. I looked it up, and Whatsapp has very little market share in the US. In China it's pretty dominated by Wechat.
iMessage, texts, facebook message, Wechat, but never a single Whatsapp user.