Late last year, the FTC put into place rules that required spammers to label any porn spam as being "sexually explicit." While an intelligent spammer might realize this is actually advertising to those who want porn spam, many feared that it would cause them to be blocked out by spam filters (rightly so... but the people using those filters tend to be the ones who don't want the spam). So, now, those less than intelligent spammers have discovered that the FTC was serious, and a number of porn spammers are being told to shut down. Of course, you could find pretty good odds on the idea that many of these spammers will ignore the order, or simply regroup and keep on spamming under other names.