Only SMS has had a massive impact on my life. Seven years ago, Meteor, my operator, introduced free Meteor-Meteor Calls and Texts. This instigated a period of huge amounts of texting between myself and friends.
Taking a small group of two dozen of my friends and acquaintances, I would estimate that hundreds of thousands of texts have been sent among us over this period. Relationships have been made and broken over SMS, and not one of us would disagree that SMS has been the most influential technology out of this list.