Is innovation stagnating in social media?

We are saturated with social media. According to statistics, 37% of the world is actively using social media. Facebook has 2bn users, Instagram 700m and even Snapchat has 301m. Instinctively, this feels like impressive uptake for something just shy of its sixth birthday. Or is it? After all, there are around 579 million people in North America, of which 71 million are Snapchat users, giving us an adoption figure of around 12% in that region. With some investigative googling, you can see that most major inventions, including the TV, the fridge etc, took about 5 years to reach half of the same region.