One thing about the success of Whatsapp mystifies me: it's tethered to a cellphone. I have a four-year-old smartphone that's basically dead, but works for gett

One thing about the success of Whatsapp mystifies me: it's tethered to a cellphone. I have a four-year-old smartphone that's basically dead, but works for getting emergency calls. I also have multiple laptops, a tablet, etc. and keep encouraging people to use FB chat (since I've given up on converting folks to Slack) to talk to me.