As mentioned above, placing ads (as part of a detailed promotional plan) is one means of providing a larger scope of "construct" that is 'compliant' with the SE's, but the hidden elements to these programs are not always truly beneficial: Google especially, has added controls and data collection metrics to their AdSense, and often links your site's ranking to the level of your program participation -- not exactly a fair metric.

Secondly, the "communities" of preferred/participating sites are not ranked fairly by the competing SE's as a result, thus upsetting the balance and relegating the performance of your website to serve narrowly cast purposes other than merit true ranking and net position based on the standard constructs and compliances....It's like the SE's saying, "Your site is not really important unless you play our game, no matter how perfect the construct or how unique and valuable your Content and overall relevancy is!"
> You can't have it both ways.......either you merit rank (and can thus sustain it independently) or piggyback the rungs as high as you can.