SAN JOSE, Calif. (

TheStreet

) -- Despite a major Black Friday boost in online shopping, shares of Internet retail giant

eBay

(EBAY) - Get Report

fell on Monday after analyst firm Stifel Nicolaus downgraded the company amid valuation concerns.

eBay shares have climbed more than 30% in the last three months, but they fell 84 cents, or 2.7%, to $30.31 on Monday as investors digested the downgrade. The company's fall outpaced the broader slump in tech stocks that saw the Nasdaq dip 1.23%.

Stifel analyst Jordan Rohan changed his eBay rating from buy to hold, citing lack of upward earnings momentum and competition from the free shipping offered by the likes of

Amazon

(AMZN) - Get Report

. The analyst also voiced his concern about margins in eBay's PayPal business.

"Margins at PayPal, while stable, could reduce total company margins over the next two years, as PayPal approaches half of total revenues," explained Rohan in his note. PayPal margins could also keep eBay's earnings guidance for fiscal 2011 conservative, he added.

According to eBay, online broker PayPal enjoyed

payment growth

of 27% on Black Friday, up from 20% a year ago. Highlighting the growing popularity of smartphones and other mobile devices, eBay noted that PayPal mobile payments grew a massive 310% compared to the prior year.

Rohan warns nonetheless that eBay investors should not get carried away with the impact of the holiday season. "Our take on holiday e-commerce is that trends have been healthy, but not beyond expectations," he explained. "In all likelihood, the seasonal trade towards retail has run its course."

Despite some skepticism about holiday season spending, Cyber Monday, the first Monday after Thanksgiving, looks set to be an extremely busy online shopping day. Ellen Davis, a vice president at the National Retail Federation, told

TheStreet

that almost 107 million people are expected to shop online in the U.S. on Cyber Monday, up from 96 million last year. The number of people using a smartphone or mobile device to shop will also increase from 4 million last year to more than 7 million on Cyber Monday, according to NRF figures.

In contrast to eBay, Amazon rival hit a 52-week high of $181.84 on Monday morning, and the online retailer's stock was up $1.64, or 0.92%, to $178.84 in early afternoon trading.

--Written by James Rogers in New York.

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