The methods spammers use is a Robot, usually a Spider style which crawls the web following various links.
They then look for POST and GET (form fields) and can generally tell what they are, as comments, etc are usually textarea tags.
They also search for a large list of keywords, such as 'feedback', or 'comments'.
As well they know the general signature to the majority of the popular blog software(s) and incorporate more information into the spider using these, and on blog sites such as wordpress, typepad, etc they all follow a general flow, which makes it easy to spider/spam them.
For instance, if you submit a query to google search for the term ".wordpress.com" you can find an extremely large number of blogs just ready for the picking.
Many spam robots can even surpass javascript tricks.
Other spam robots can read images and surpass simple CAPCHA implementations, hence why the letters on good ones are warped with a solid grid going through it.
This is as much as I can tell you.. I don't think seeing, writing or using a spam robot will help with defend against it; at all.
And you will have a very hard time to get anyone to assist with finding / making one, im pretty sure..
Regards,
