How can a computer evaluate the 'realness' of a review? The idea of Yelp, crowdsourced business reviews, is great, but do we really prefer trusting super active web content contributors, seeking cyberspace attention, over experts (eg Zagats)?
They're afraid of competitors leaving negative reviews for a business and there's probably something to that, but there's no transparency about it. And they've been doing the extortion thing for a while now: http://dealbook.nytimes.com/2010/03/19/yelp-under-fire-from-...
I always thought it would be great if there was a Yelp for landlords - because landlords are rarely held accountable and it's not like you ask for references before you sign a lease - but there would probably be too many false reviews posted to make it work or tenants wouldn't feel comfortable speaking freely (because unfortunately tenants still need references). There's actually a website trying it, but doesn't seem like it's going anywhere right now: http://www.donotrent.com
Hopefully people will see Yelp for what it is: a small sample of the population that may be dissimilar to you writing probably biased reviews.