See my 2010 paper "'Places' spam - the new front in the spam wars." As I wrote back then, "The two phases of spamming Google Places are the insertion of fake business locations and
the creation of fake reviews. Both are embarrassingly easy." That hasn't changed.
Google doesn't fix this 4-year-old problem because Google makes money from bad search results. If search results take you directly to the business selling whatever it is you want, Google makes no money. If you're detoured through some Demand Media content farm, Google makes ad revenue. If you get fed up with being sent to ad-choked sites and click on a Google ad, Google makes money. Organic search that sucks is a fundamental part of Google's business model.
Technically, it's straightforward to fix this. Business data has to be checked against sources businesses can't easily manipulate, such as business credit rating companies. A business that reports fake store locations to Dun & Bradstreet or Experian will soon have a very low credit rating.
Bing or Yahoo could beat Google at search quality. They have the same spam problem, but it doesn't make them money. That's because Google has most of the third-party advertising market. Web spam on Bing drives traffic mostly to sites with Google ads, not Bing ads.
The real search engines are Google, Bing, Baidu (China) and Yandex (Russia). Everybody else, including Yahoo, is a reseller. Yandex has been doing some interesting stuff lately with linkless search ranking, and Baidu just opened a Silicon Valley office.
Yahoo's Marissa Mayer announced last January that Yahoo was getting back into search. (They've been reselling Bing since 2009.) That appears to have been a bluff to get a better deal from Microsoft. There's no indication of Yahoo actually building a search engine. No relevant job ads, no data center buildout, no increased crawling by Yahoo bots, no high-profile hires, no buzz in Silicon Valley.
Bing ought to be doing better than it is, but they're reported to have management problems. Every year, there's new top management at Bing, and it doesn't help.