If you decide to edit Wikipedia without creating an account, think you're anonymous? Think again. As the essay "IP edits are not anonymous" explains, the reverse in fact may be true.
Any edit made when not logged in to a user account is automatically identified with the IP address it is coming from. If you're a residential customer of a giant like Comcast or Time Warner, and you're not doing anything that would be cause for a subpoena, there is some safety in numbers. But if you're editing from a corporate, educational, or institutional computer, there is a very good chance that your edits can be traced to it, even with simple tools anyone can access.
If you create an account, Wikipedia editors will certainly be able to identify your edits to that pseudonym, but so long as you're not using multiple accounts deceptively, your identity remains your own secret.