I get the same problem with a mail account. There is no spam filter. And not only do they spam me EACH AND EVERY DAY, but also do they do it from different gmail accounts each day. It means these Son........es always keep the SAME EMAIL DATABASE even if they already sent you like one thousand emails without getting any reply ! Theses guys should just not exist...
i was gonna join in with talks of blo$jo8s and spam, then Sam drops the L bomb. did you find a method of stopping them?
it is possible to stop them completely. i once had the same problem with a phpbb forum. after installing a good captcha mod (for registration and guest postings) they were gone. best captcha mods work with individual images or questions, means you define them and change them. never use standard questions that can be answered with yes/no. after 2-3 months the bots didn't even try to visit my site.