What use are Hidden Links?

It's a pretty obvious question. "Why create a link from one web page to another, only to hide it so nobody can find it or click on it?"

Well... You see, it's like this... A number of years back, some bright spark figured out that a website's internal links, and the words associated with these links [anchor text], played a vital part in the way Google would assess its relevance to a given search term.

What basically happens is that the search engine uses the link's anchor text to give it an idea of what the web page it leads to is actually about. And, since the link is not only entitled Unethical SEO, but also leads to a page which actually contains some information about it, the search engine perceives it as a relevant reference for this term. So, the more links, entitled Unethical SEO, I have pointing at the web page in question, the more relevance I accumulate for this term in the eyes of a search engine, which is as it should be, because it is relevant.

Simple, yes? So just exactly what is there to be gained by hiding links?

The thing about filling a web page's content with a load of visible links to other parts of that website, is that it tends to distract your visitor's attention from whatever it is you actually want them to do.
On the one hand you want to increase a web page's relevance in Google's eyes with as many links as possible, but on the other hand you don't want to distract your visitor while you're trying to sell them something, so you simply make both links and text content the same color. The theory is that Google will be impressed by the links [until they detect the setup], and the visitor is not distracted by them.

This is just another attempt to fool Google. Remember: Google wants to see exactly what humans see.