It is nice to be able to connect with people who do not live or work close to us, but it is counterproductive when that means of connecting removes us from the folks who are right next door or who live with us. The side effects of a digital life are often that we neglect to have an actual life.
Yes, there is a huge side effect to spending a bunch of time on a digital program such as sitting behind a computer or playing a video game. You lose out on the real world. And getting to go and do things that actually help you in life to enjoy.
In some cases there can be side effects to leading a digital life. Some people can be less social and depend more on digital aspects of life than others. This isn't true for all people, but for some it can be the case. They may not go out and do more things online or using digital means.
People need to understand that our brains are plastic and when you repeat things often enough and live a specific way long enough, your brain rewires itself. This is what has happened with the digital lives we lead now. There is less of an attention span, and we don't memorize nearly as much.
I do not believe there side effects to having a digital life. Life on the Internet, now that it's not anonymous, is much like life in the real world. It has many of the same drawbacks and consequences that you see in normal everyday life, so I believe there is a big gap closing in on the Internet and its relate-ability to the real world.