I think as far as hurting the kids with the skill of communication - yes. Not targeting just social media, but this also includes text messages, forums and emails. If I ever turned in anything written that included things like "u" for "you" and the wrong use of "there, their and they're"... the paper would fail. Today, people aren't held accountable for their communication skills, and you find more than anything that it is normal for people to spend time deciphering the emails from others. Communication is the key to being successful in the working world, and this is one reason (out of many) that social media and networks are hurting kids.
Of course cyber bullying, the immediate access to whatever you want without the skill to sort what is real and the inappropriate content that is delivered within seconds are also reasons social networks are hurting the kids - but that would turn this answer into a thesis paper.