[quote=@Ellri]
y'know... if you want to make a truly sneaky spambot... have it post regularly the first ten posts, then in the 11th, make its top half regular and the bottom pure spam... Or somesuch other convoluted system that is as not beneficial as spam from post #1.
[/quote]

Sounds easy to a human, but pretty complicated to do for a computer. For it to be completely automated, you'd need some heavy horsepower for the calculations the script would need to do to "learn" what makes up a normal post on this site. It's a pretty complex field, also known as "machine learning."