I would add: WhatsApp was there, free and very well done. Even in countries that had free domestic text messages (where the “free” factor was much less importa

I would add: WhatsApp was there, free and very well done. Even in countries that had free domestic text messages (where the “free” factor was much less important), WhatsApp nailed group messaging better than anything else available at the time. Also, by using phone numbers they skipped the entire “create account / invite friends” stage, making for a much smoother bootstrap.