I think that technology has stunted the intelligence growth of most teens and young adults. Too much dependence on spell check, calculators, websites like this, etc. Most cannot spell correctly, do basic 5th grade math and are not willing to do homework or read books because they can get the answers on this site and others.
The disadvantages that the technology has for teens are that there is no such thing as privacy hence exposing the teen to wrong things like pornography. Technology has made teens lazy as they keep on playing games or chatting and prevents them from learning the important concepts of life.