If you believe that Yelp should be barred from preferential reviewing in your jurisdiction, talk to a legislator. (I would agree with you and vote to that effect in my own.)
One possibility is that their competitors don't have friends in very high places. Uber is stinky but as you point out hardly the stinkiest. But Uber clearly has very powerful enemies.
That being said, I rarely bother opening yelp since I'm usually on Google maps in the first place and in my area they have plenty of reviews.
I'm not sure about the actual situation with Yelp, but as long as they're not making up negative reviews (which could be slander), it might be ok, legally. Given their size in that market, anti-trust concerns might come into play, though.
I don't think Google is so bad. They're just doing what's good for their investors.
Why aren't the authorities going over the ACTUAL, honest-to-god mafia startup? Sorry, I realize it's off topic here, but my first thought when I read "Justice Dept begins criminal probe" -- was FINALLY!
We all know which company I'm referring to. And all I said was "employs mafia tactics and forces businesses to pay a protection fee, or actively fucks them up and attempts to hurt them". There's only one company like that in our "community". Why are they allowed to behave that way with immunity?
(Sorry to hijack this thread. Also, I have no disclaimer to make and am not associated with either company.)