AccountKiller’s a pretty simple tool to use and understand: it’s a site which shows you where, in many prevalent social services, to delete your account. It also acts as a ratings bureau for the ease of use for those services. There are three levels: black for hard to delete or undeletable accounts, grey for difficult but doable, and white for easy.
For example: Facebook’s rated grey, because its ease of account deletion has strings attached (in my experience, you delete your account and then be sure to not accidentally click anything from facebook—no easy task—for fourteen days). iTunes, on the other hand, is rated as “black” because there’s no account deletion link anywhere on the web; you need to email Apple and tell them to do it.
The upside of being invisible online: nobody can track you. The downside: you have no reputation. Neither is right, neither is wrong, but both come with social consequences. My advice: attach your real identity to the services you stick to with relevance to who you are.
For example, if you’re a lawyer, having a publicly-viewable account at The Pirate Bay, I’m going to assume you’re not that attentive of a lawyer. You might want to call yourself something more anonymous there—or live your life in a moral binary where you are always exactly what you say you are.