This image is just an example of the multiple identities on the internet. The people above can be seen as a representation of the stereotypical users or creators of the stated sites, but are also colour coded to their logos.
With the communities that come with these digital identities, boundaries can be crossed. For example recently it has come to light that some Youtubers have emotionally and physically abused people, some being fans. http://www.dailydot.com/fandom/tom-milsom-underage-sex-scandal/
Also communities may not always mix together well and online feuds can be created. A notable example of this was the 4chan vs Tumblr argument.
With these digital identities it is also possible for people to create new identities for themselves, sometimes for better sometimes for worse. But this action is often taken advantage of and thus the creation of Catfishing was created. "A catfish is someone who pretends to be someone they're not using Facebook or other social media to create false identities, particularly to pursue deceptive online romances." - http://www.urbandictionary.com/define.php?term=catfish
Actual identities can also be ruined on the internet, as once something is posted it is there forever. A good example of this is Jessi Slaughter. http://knowyourmeme.com/memes/events/jessi-slaughter
For the future, I don't think it'll be possible to have an identity without being online. People used to ask "What's your number?" but now its "What's your Facebook or Twitter?". I think this will be more so in America due to a lot of social media sites being made in America by Americans. One day our whole identities could be online. Another Scenario is the storyline of the film Her, where a man falls in love with his operating system, a few years into the future. Before this his presence online was much greater then it would be now. It could seem like he was inside the computer when playing games for example. If it was possible to simulate a game around a room it would also be possible to simulate people around, there would no longer be a need for physical interaction. It would be even more possible for meetings and lectures to be held over Skype, more so then what is being done already.