I think the best deterrent against spammers is to make your service unattractive for them. This is quite hard if you are creating a webmail platform, but luckil

I think the best deterrent against spammers is to make your service unattractive for them. This is quite hard if you are creating a webmail platform, but luckily most of us aren't. Hide down-modded comments, surround outgoing emails with descriptive templates, etc.