While OP has many valid points, I think we need to remember that most human inventions have been met with criticism.
Such criticism has often proved to be over-stated, but to contain some measure of truth.
However, it is the use we make of our inventions that usually determines whether they are good or bad, as already stated in this discussion.
People may not continue using social media to the extent they do now, where we are barely out of the "honeymoon period", but social media are undoubtably like the telephone and TV here to stay.
We need to educate each other regarding the social conduct expected when using these media.
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It used to be considered wrong to send an unsigned communication of any kind - now, on social media it is the norm.
This must not, however, allow us to be offensive, lie or publilsh unverified statements - all of which we have seen happening on the "new" media.
If children are too young to understand the potentially harmful content of what the are posting, then they should not have access to social media.
After all, we don't let toddlers play with matches, do we?
It may be harder to prevent a 13 year old publishing something they shouldn't than prevent a 2 year old get hold of a matchbox, but parents and teachers have a responsiblity to ensure that these things don't happen.
Cyberspace is being policed, and actions can be brought against adults who are being offensive or committing crimes via social media.