Fannie Mae and Freddie Mac backed off from their heavy advertising activities during the second half of 2004, marking the first time in several years that the GSEs appear to be starting to pull back from their aggressive public-relations strategies. According to TNS Media Intelligence, a research firm that tracks advertising spending, Fannie spent a respectable $54.6 million on advertising last year. This marked a 25 percent decline from 2003, when the large GSE laid…