Here's a question for you, and I don't know the answer: It seems true that everyone has a "writing fingerprint" but is it not the case that it would change ove

Here's a question for you, and I don't know the answer: It seems true that everyone has a "writing fingerprint" but is it not the case that it would change over time? For example, is it not likely that my writing style at present is more similar to that of another person on the Internet than it is to my own style 7 years ago? Moving targets would complicate Internet-scale de-anonymization considerably, because you'd have to take "ancient" Usenet posts with a grain of salt. This would be even harder if people learned to mask their writing style, perhaps using "translators" designed to thwart the de-anon technologies. Note that the amount of information you need is always logarithmic in the potential number of authors, and so if you can do 200 authors you can almost definitely push it to a few tens of thousands of authors. This makes sense from an information-theoretic, big-picture standpoint, but I'm guessing that the amount of actual data (measured in text, not information content) per candidate required to identify an author among N candidates is somewhere between O(log N) and O(N)-- my bet would be O(N^k) where 0 < k < 1. The reason is that, while your "since/because" example might be a great fingerprinting measure, there are only a small number of great (high information content) measures like this, then there are some few higher-hanging fruit, then a lot of scraps. It seems that any attempt to identify an unknown person among 1M+ candidates is going to require using the scraps, and it's not clear how much information content there is in them.