I've done some more investigation in Lott's latest explanation for his Mary Rosh postings:
I originally used my own name but switched after receiving threatening and obnoxious telephone calls from other Internet posters.
The first group of Lott postings were made between 3 June 1998 and 14 July 1998. All the responses were polite. In one of his postings Lott complains about getting threatening phone calls, but not about phone calls from other Internet posters.
You ought to see what happens to my telephone calls when someone like a Charles Schumer or Josh Sugarmann or Sara Brady makes this charge. I get lots of threatening telephone calls and letters. These calls don't bother me, though they do greatly upset my wife.
I asked David Friedman, who introduced Lott to Usenet, if Lott had ever mentioned something as highly unusual as getting threatening phone calls as a result. David could not recall Lott ever mentioning such a thing.
After 1998, there was the Mary Rosh review of More Guns, Less Crime in 1999. The next Mary Rosh posting was this one, on 2 June 2000 in freerepublic.com:
If you want to read the research paper upon which this research is based, go to:http://papers.ssrn.com/paper.taf?ABSTRACT_ID=228534
The papers that get downloaded the most get noticed the most by other academics. It is very important that people download this paper has frequently as possible.
Mary Rosh joined freerepublic.com that same day. It seems that Lott was reading freerepublic.com and came across a posting of one his articles and decided to try to boost his download numbers at SSRN. Obviously he was in no danger of getting threatening phone calls from freerepublic members. The reason that he posted under a pseudonym is that trying to rig the download counters as Lott did is against the rules at SSRN and Lott did not want to be caught doing it. Mary Rosh posted several more times to freerepublic, usually trying to get people to download papers from SSRN.
In July 2001, Mary Rosh made similar postings to Usenet, once again suggesting people download Lott's papers from SSRN. However, unlike freerepublic.com, on Usenet there are posters who disagree with Lott, so her postings drew comments that were critical of Lott, Mary leapt to Lott's defence, and Mary's Usenet career was launched.
Far from being concerned about threatening phone calls, Lott also posted to Usenet under his own name while Mary was posting. He also posted a few days after Rosh was unmasked, and even posted yesterday.