I am terrified by the fact that so many other people don't think twice about handing their toddler a smart device. Every time we go to dinner, there's a table nearby with a tablet planted in front of a child in a booster seat.
"There's no evidence that it's harmful", people say, but how could the evidence possibly exist? It would take 16+ years to do a thorough study (possibly longer), but smartphones have only been popular for half that time. And people have only been using them as babysitters for the past 3-5 years, at most.
We may not know the true extent of their damage until it's far too late for the affected generation. There's always a chance that the damage will be minor and/or reversible, but most people don't seem to grasp the risk they're taking.