A real spammer will take any link, it doesn't matter if the link won't be considered as some form of endorsement by search engines due to the use of the rel=nofollow attribute. A spammer will happily post a million links, there will be some poor souls out there and click on some of them. Quantity over quality has always been one characteristic trait of spam.

Spam and link spam were already there before Google existed and the PageRank was invented. The index of the AltaVista search engine was huge and full of spam.

When the nofollow value for the rel attribute was introduced there were many claims that this would reduce the amount of link and comment spam. Critical remarks came often from people who were offering link building and SEO as a service.