I think Stephen Albert was asking about the possibility of using logs to find out what he's reading, not posting. That's quite possible. Recall the recent incident when an unethical researcher looked through his colleagues' .newsrc files to see what newsgroups they were subscribed to.
Most NNTP sites run INN, the software I wrote. (You can find out by doing "telnet {the_news_host} 119" and then looking to see if it says InterNetNews in the greeting line.) By default, INN logs every group command -- every time you switch to a newsgroup. It logs the full IP address of the client. If it can forward-and-backward map the IP address to a hostname (i.e., ipaddr->host and then gethsotbyname() includes ipaddr as one of the host's address) then it logs by client hostname. It is trivial to turn on full logging at compile time, boot time, or per-connection via a management program. This will then log ALL interactions. I could imagine that without too much work, someone would turn on logging for a given set of addresses (say, anyone in the "default" category). Every day INN generates a report that includes the host/ipaddr of every host that connected, what the most popular newsgroup categories are, etc. Hope this helps. Relevance? You're being watched. /r$