Okay, here's the theory. Every page on the interwebs has a low inherent page rank score.
Page rank passes through links like water through pipes.
GSA ===LINKs===>MONEY SITE = PENALTY
GSA===LINKS===>TIER 1==LINKS=>MONEY SITE = TIERED LINK BUILDING
You essentially get links to your site on a 3rd party website, either someone elses (real douchebag thing to do) or a Web 2.0 property, these are known as Tier 1 links.
You then use GSA to SPAM THE LIVING HELL out of the site that is linking to you. The idea being that you channel page rank from a TIER 1 site. The negative impact of the spam is filtered through the TIER 1 site and your site gets a boost.
What I have just described is a very basic description of the setup, in actuality, it's more complicated than that. but that's the gist of how it works.
Factors to consider are multiple tiers of links. anchors text patterns, link velocity.
That's all I'm giving away, emphasis on the "douchebag" comment above.