There are at least FOUR ways spammers link build and hide the links, all of which previously worked successfully on all search engines, but are now penalised by the google algorithm which is clever enough to find them (unlike Yahoo? and Bing?)
1) Hidden Text which forms a link, and is the same colour as the background
2) A link that does not react or change colour when the mouse cursor passes over it, so the user does not know it is a link
3) A link that is disguised as a button, which does not react when the cursor moves over it (mouse over).