OP, just in case you want anonymity, because you are planning to commit online crimes, I have an advise for you:
Everything that looks anonymous to you now, doesn't necessarily mean, that it still will be in the future.
Take the dna evidence as an example. Some "perfect crimes", weren't that perfect anymore, after this invention.
if too much time pass then the criminal is acquitted because of prescription, so this is moot, also it's not like anyone who want to stay anon has committed a criminal activity
there are certainly other reasons to want to preserve your identity