I just checked my Google PageRank. It's a 3 of 10. That means it's six orders of magnitude less important than Amazon.
If I were running for class president, I'd be just behind the kid with the perpetually runny nose, in terms of popularity.
If I were running for ranks on the keyword "paul allen yacht octopus," I'd be behind a bunch of spammy, auto-generated sites that recycle each others content and participate in shady, reciprocal linking schemes. ("This link systems uses a trapezoid!")
As it happens, though I'm not really running for ranks on that keyword, I am ranked behind those spammy sites. Those shady link schemes work, by and large. For spammy sites.
Why only spammy sites? If they work for those sites, why not for your big business?
Because those spammy sites are not individually important to their owners. They are like bubbles on the ocean. Individual bubbles can come and go, but the foam remains. Any single spammer will have dozens, hundreds, or even thousands of sites that each contribute a tiny bit of revenue to the overall operation.
Businesses put their eggs all in one basket. One website. One shot at rankings and revenue. Play with fire, get burned, and go out of business.
There are safe ways to get free backlinks that won't destroy your site. And there are lots and lots of dumb ways to get links that just might completely hose you.
But, as I have said before, I don't have to care about this anymore. I'm mostly just writing this for the money. This is a Pay-Per-Post post, of the sort which I anticipate writing every couple days until I've saved enought to buy a Wii. :o)