That right there: bingo - that's why I think that Yelp is coming out on top of this. They're delivering value to the website visitors/app users. Not that either company is a paragon of virtue, but compare Yelp to Apple and yourself to an iOS app developer and I suspect you'll have an accurate picture of who's where on the totem pole (cf Gruber: http://daringfireball.net/2010/05/nack_control ).
If Yelp were dedicated to making its advertisers happy, it would quickly become useless for its users.
I'm not saying they don't provide a valuable service. I'm saying they won't be able to exist without making a profit, and angering the people you're trying to get to write checks is a poor way to go about growing your business. There definitely has to be separation between the advertising and reviews - because validity of reviews is top priority, but their system, from my first hand experience, and discussions with many other businesses owners is skewed too far in one direction at the present time.
They are bleeding money, and they're forecast to do so for the near future. Bottom line is they need to figure out a better way to make money off what they do, or improve their value proposition for those customers who are generating the revenue.
If Yelp were dedicated to making its advertisers happy, it would quickly become useless for its users.