> In this case I trust Google because their incentives are aligned with advertisers
Is it?
The better the overall search algorithm, the less the need to hack around it by paying for placement..
Some level of 'bad results' helps ensure that ads are needed in the first place,
and junk sites provide a ready source of bad results..
Now, when junk sites cause you to lose revenue, the equation gets unbalanced,
but that is not to say having the variable equate to 0 is good either, because the revenue would lessen..
Obviously it can't simply allow the fraud because that would make google fraudulent itself, but at the same time they cant just outright ban crappy sites, since there are so many that are only marginally crappy but otherwise legitimate, and could only be unwilling participants in someone else's dishonest scheme..
I would argue that google is attempting to maximize a set of equations here, and since at some point there is a grey area between 'crappy scammish sites' and 'full on fraud', google has some leeway to what extent it polices the grey area, and, further, to some extent can do this at advertisers expense so long as 'the house wins' to borrow gamboling terminology..