While the United States as a whole tends to be an indivudualistic, independent society that focuses heavily on who we are and expectations for what we are "supposed" to be, we also enjoy our fair share of remaining anonymous for a variety of reasons. Perhaps you're simply venting but you don't want to start an argument, so you leave out the name in the hopes that some measure of privacy will help. Or perhaps you want somewhere to voice your thoughts- here I'm referring to more of the online community, especially places like Tumblr- in a place where there will hopefully be a wide variety of responses that you may not have even considered outside of the community in which you live. Or perhaps you're braver behind the screen, and use that to do things that would be otherwise unpleasant or maybe even unwise. Whatever the reasons, there are pros and cons to going unknown.
Pro: There's some pressure off your shoulders.
If no one knows who you are, there's a little more room to be liberal with what you say without worrying quite as much about the consequences, although they're rarely nonexistent.
Con: Some people feel a little TOO weightless.
Being unknown can make people braver to the point where they do things or say things they wouldn't do if their identity was known. Internet bullying is a prime example here. Particularly because we can't see the person's immediate reaction to a message, we as people don't feel as much pressure to be aware of what we're saying. That can make it easy to become vindictive and even cruel on the internet towards people one has never meet and likely never will.
Pro: Finding information without judgment.
Naturally there's search history, but most of us don't have other people digging through our computers I hope! Looking for information and wanting to learn and hopefully grow as a person or simply sating curiosity is in no way a bad thing, but asking the wrong question to the wrong person can be dangerous in a face-to-face situation. Chances are, someone else is wondering the same thing, so looking it up and giving one a sense of anonymity isn't a terrible thing. Not only is information now more accessible than ever, but it is also now able to be obtained without fear of judgment, generally speaking.
Con: Stalkers, kidnappers... you get the idea.
Just like people are capable of doing great things, we also have the abilities to do some pretty awful stuff if our moral codes allow it. Kidnappers, rapists, and stalkers, not to mention people that are generally out to damage others, are all on the internet with the rest of us that have less harmful intentions. I once heard about a girl who wanted to see how many people she could talk into killing themselves. Terrible, right? While she doesn't necessarily hide under a fake name that I know of, using the internet and having some distance from her and whomever she is speaking with means whatever she does, this girl believes that it won't impact her. Whether that is right or wrong, I'll leave my opinion unsaid, but she isn't the only one who thinks this way. There's a reason we grew up being told not to meet internet strangers and to be wary of the internet in general.
So all in all, it can give a sense of security, but it can also be used to overstep societal boundaries that would normally be considered varying amounts of appropriate. I usually lean towards remaining anonymous concerning matters in which I am incredibly nervous or I'm just venting to no one in particular and would rather not receive some sort of lengthy response. But whatever the reason, it's worth being wary. Just because your motives are innocent, doesn't mean everyone else is the same way. But please don't take that as me telling you to be afraid! Sometimes exploring is the best part, right?