This New Yorker article points out that the answer depends on what you mean by "we." Does that include you and your smartphone, or just you?
http://www.newyorker.com/online/blogs/elements/2014/01/if-a-time-travell\ er-saw-a-smartphone.html <http://www.newyorker.com/online/blogs/elements/2014/01/if-a-time-travel\ ler-saw-a-smartphone.html>
