I am a Nobody and therefore use my real identity!
The reason people do not use their real names aside from the reasons already outlined is to ensure the freedom of speech or rather the written word without the fear that it may bounce back on the writer negatively.
On this site all polite, non offensive, non-breaking-of-halacha etc etc opinions are allowed and everyone has an opinion some stronger than others and this site allows them to express their views and comment onwards.