[WhoIsSatoshi]

there is no end to that argument, if a spammer is good enough to be able to foresee anti-spam software then they are likely beyond the target audience. BUT the average and by large general spam crew are not technical experts, most of them have bought some software to advertise to a large audience by mass email / crawl / filter, and are just looking at monetizing some product (or get your infos / CCs). By wasting time for the 95% of the spammers (ironically with techniques that are very similar to them) you can still weed out a big chunk of that sector and have a big impact.