As the popularity of consumer review websites continues to climb, so too do the complaints about their reliability and fairness.

While experts differ on how "grassroots" many of these reviews are, there's no denying the influence they are wielding on the way consumers choose products and services.

According to a survey conducted by the website Search Engine Land, a site devoted to news and information about search engine marketing and optimization, 72 percent of consumers surveyed said that they trust online reviews as much as personal recommendations, while 52 percent said that positive online reviews make them more likely to use a local business.

One of his charts shows that 70 percent of restaurants in Seattle are on Yelp whereas only five percent of restaurants have been reviewed by all other media sources.

Fake reviews

Looking at the 100 most popular books over a two-year span, one can find a correlation in the reviews overall but also areas where they deviate.

For example, professional reviewers tend to be more generous to authors who have received other media attention. While consumer reviewers are more favorable to first-time authors.

But the accuracy of the reviews on these review sites has increasingly come under scrutiny. The owner of a Vancouver electrolysis chain recently accused Yelp of filtering out positive reviews about her company.

Yelp denied the charge but does admit that its filters wean certain reviews from a site that they think are spam or fakes.

Most consumer review systems include a hierarchy of reviewers. The so-called elite reviewers usually have a higher status on a website, their reviews are displayed more prominently and given more weight.

These elite reviews act somewhat like a screening mechanism. On Yelp, the elite reviewers have a lower variance in the reviews they leave, meaning the non-elites were more likely to rate something either a one or a five, while elite reviewers tend not to be at the extremes.

Spam reviews remain a problem in the industry.

Yelp filters out 15 percent of all its reviews.

Google said it has created a new algorithm to detect fake reviews. Based on how quickly certain reviews pop up, they say they can discover which reviews have been posted by spam or whether someone was paid to do it.