While WhatsApp started as a way to set status ("Can't talk, text only", "Urgent calls only", "At school", "Busy"), the eventual razor-sharp focus by Jan Koum &

While WhatsApp started as a way to set status ("Can't talk, text only", "Urgent calls only", "At school", "Busy"), the eventual razor-sharp focus by Jan Koum & Brian Acton to replace SMS (not MSN/Y! Messenger, not BBM, not IRC), in my eyes, made it the juggernaut that it became, inspite of the many regional/global clones. - No logins. No sign-ups. Mobile phone number was the username; SIM card, the password. - No central database of messages. No backup & restore. No stickers. No web-based access. Only fast text-based relays. For phones. - Aggressive cross platform focus. Including clients for Blackberry & Symbian, not just mainstream OSes. - Little to no perceptible downtime. Worked just fine in all sorts of flaky networks. Consistently and reliably. - No ads, no spam. - As cheap or cheaper than SMS (£1/yr), but works & roams globally. - Voice notes and media to expand beyond the Anglosphere. Another tidbit I find interesting: Jan used the fact that every time an app's title / description was changed, it would show up at the top in the "new" category of the iOS App Store, to help reach a wider install base. In short, being laid off from Yahoo! to being rejected by Facebook, brought the best out of Jan & Brian. They ran a very unconventional SV startup and got a lot of the details exactly and deliberately right. Not many stood a chance, as evidenced by their eventual £22bn exit.