50 years from now, we will look at people's addiction to cell phones like we see the addiction to cigarettes in old black-and-white movies. The negatives so far have been (sources: https://markmanson.net/smartphones ) and ( https://www.gq.com/story/cal-newport-digital-minimalism )
(a) shorter attention span. Rather than spending a lot of time to understand a subject in depth that are "Too Long; Didn't Read" (TL:DR) people are now satisfied on quick short answers and soundbytes. While technology has made Wikipedia and a vast amount of information readily available, people are not as curious as they should be to take advantage of this.
(b) less face-to-face interaction with others. Communication face-to-face is a lot different than via text messages or tweets. A lot of information is communicated non-verbally through smiles and hand gestures that just don't get across with abbreviated texts and emojis. Video calls are more effective, and technology is now making these possible.
(c) limiting your experiences to the "echo chamber" -- technology now can help people limit what they hear and see to only those things they already agree to. Customizing news feeds, and relying on Facebook of your closest friends will not expose people to new things, new experiences or new ideas. While technology can be used to explore the world from your home, not everyone takes advantage of that.