Spammers Motivation?

When speaking specifically about email spam, generally it is accepted that about 1 click in 1,000,000 emails is all it takes to be profitable. It is so cheap and easy to automate the process, that all they need is a very small number of people to believe that they will make money when they help the recently deposed Nigerian Prince. On forums it can be a little more difficult as there is additional security they need to bypass ie the ability to create accounts automatically or actually make the accounts manually. In this case the threshold may be closer to 1 in 1000, but if there are 1000 people actively using this forum, it only takes one who thinks they can get rich by helping the Nigerian Prince to make all these gibberish messages worth it. And in some cases people are trying to generate advertising money from clicks. With youtube, everyone who watches (even by accident) is more money in their pocket. Some do not care if the sports video is absolute garbage, if they get enough people to click on the link, they make money.