Here's a good definition from sapphospeaks :-
"The real social chameleons that go from person to person being all things to all people are simply a blank slate in reality. They are either so damaged or so stunted that at some point in their growth they simply shut down and adopted a malleable yet likable persona – a simpleton of sorts that layers could be added or subtracted to depending upon the situation. The layers become a bit thicker through the years but the true person never changes and the values or belief system that make up anyone are simply not present in this core. It is built into the layers – layers that on some issues have both the positive and negative viewpoint to fulfill everyone’s dream for the perfect friend or lover."
"The real social chameleons that go from person to person being all things to all people are simply a blank slate in reality. They are either so damaged or so stunted that at some point in their growth they simply shut down and adopted a malleable yet likable persona – a simpleton of sorts that layers could be added or subtracted to depending upon the situation. The layers become a bit thicker through the years but the true person never changes and the values or belief system that make up anyone are simply not present in this core. It is built into the layers – layers that on some issues have both the positive and negative viewpoint to fulfill everyone’s dream for the perfect friend or lover."
Every article has a different take on this. It can be both good and bad depending on the situation. I'm not saying that it's bad to be a Social Chameleon, having mentioned that. It's good if we know how to interact and blend into different crowds. In my case, I always tell myself to limit from being too comfortable because not many people can be trusted. And for some, it can be an unhealthy competition with themselves wanting so hard to be 'in'. Here are my points :-
1) A Social Chameleon is not at all a bad person. I guess one just feel the need to fit in and be equal with anyone else in the group/clan.
2) Reason one becomes a Social Chameleon is maybe because that this person never experience the 'glory' of high school life -- that a person wants to be noticed at least once in her/his life.
3) I truly believe that in private, Social Chameleons have low self-esteem and fear of being alone/rejected. Thus, they need to be around people who make them look (or/and) feel good.
4) True personality of a Social Chameleon is often undefined.
5) Social Chameleons may want people/the public to take notice of them and their social lifestyle.
6) Sometimes, their actions are not intentional. They may feel like they are already in a comfortable stage to act as the person they think they are - yet are not aware of it.
Do you know anyone who is a Social Chameleon?

