No Subject

How "anonymous" (to what degree) are email messages sent through the various remailers (Mixmaster, EFGA, ml.org, etc)? Have there been any studies done as to the degree of anonymity obtained from using these remailers? (I haven't been able to find any.) And does anyone know of any studies being done in determining whether or not content-based analysis - diction and language - is a reliable way to determine identity? It seems that if Dick has a certain vocabulary, uses a certain sentence structure, etc., and regularly posts using a nym, that this form and content could be traced to Dick, so the likelihood of the post coming from him and not Jane would be that much increased.