In many respects
SEO has become like product placement in films. Do the stars really prefer brand X to smoke, drink, drive etc? Of course not. The brands pay to feature in films. Now the brands pay to feature on the SERPs. Either through an intermediary
SEO or through pay per click.
All the SE's have become corrupted. It's just a question of degree and definition. Spam is an arbitrary definition of illicit manipulation. Sure there's crude black hat. But most
SEO involves shades of grey where one man's spam is another man's garlic sausage. Given the combined market cap of Google and Yahoo is close to $200 billion it would be a surprise if everything stayed clean and above board.