David Einhorn, founder of hedge fund Greenlight Capital, told investors on Monday his investment firm had taken a position in business review website Yelp (YELP) - Get Yelp Inc Report, saying he thought the company was undervalued and could double revenues by 2019.   

While Einhorn might be long on Yelp, Jim Cramer, the founder of theStreet and manager of the Action Alerts PLUS Charitable Trust Portfoliodoesn't agree.

"I think Yelp's not as good as it used to be because Google changed the [search] algorithm, which makes it so [Yelp's website] isn't found as much," Cramer said, referring to changes the Mountain View, Calif.-based search engine giant made recently. "That really hurt the stock."

Cramer did acknowledge that Yelp has a recurring revenue stream, calling it the "the Yellow Pages for restaurants."

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Yelp is scheduled to report its first-quarter earnings next Tuesday. In February, the company estimated revenue of between $154 million and $157 million, an increase of about 31%. For its 2016 revenue, the business-rating behemoth said it expected to bring in between $685 million and $700 million.

In its 2015 annual report, the website operator posted a $32.9 million loss on $549.7 million in revenue last year. The firm's revenue increased by almost half compared to its full-year 2014 revenue of $377.5 million, which would be a 26% increase from the revenue Yelp brought in last year.

Cramer also panned Yelp's interface, saying it hardly left the website's visitors with a positive experience.

"I didn't expect that the user experience would be so junked up," Cramer said. "[Facebook (FB) - Get Facebook, Inc. Class A Report founder and CEO] Mark Zuckerberg talked over and over again... how user experience is the most paramount thing. [Apple (AAPL) - Get Apple Inc. (AAPL) Report CEO] Tim Cook always talked about user experience. There's a hideous user experience with Yelp, one of the worst, and that's what I think has really hurt it, plus the Google algorithm."

Facebook announced its first quarter earnings on April 27, bringing in revenue of $5.4 billion, an increase from $3.5 billion the same time last year.

Apple reported earnings April 26, posting its drop in revenue in 13 years and its first drop in iPhone sales ever. The company brought in $50.6 billion for its second quarter and sold 51.2 million iPhones. Apple reported earnings of $58 billion and sold 61.2 million iPhones the same time last year.