Does purchasing CNET really help CBS?

(Fortune) -- With its bold $1.8 billion purchase of CNET, CBS is making a play for ad dollars that are shifting to the Internet. But the company may be paying too much for a network of Web sites that won't address the conglomerate's main problem: an over-reliance on advertising dollars as a source of revenue.

CBS Corp. President and CEO Leslie Moonves announced Wednesday morning that the company will make a cash tender offer to purchase CNET Networks Inc. for $11.50 per share, or about $1.8 billion. CBS will add CNET to its collection of media holdings: a TV broadcast network, 29 local television stations, outdoor advertising displays, 140 radio stations, cable channels such as Showtime, and Simon & Schuster publishing.

CBS management touted various "synergies" that the acquisition will unlock, but on the conference call with investors Thursday, executives offered few specifics. In a release, Moonves pointed out that the CNET deal would give the company exposure to the "fastest-growing advertising sector" - Internet advertising.

The acquisition takes place against a backdrop of slower ad spending. Overall advertising outlays grew at their slowest pace in five years during the last quarter of 2007, and that pace is expected to continue, according to Bernstein Research. Internet advertising grew 27% during all of 2007 to $25.5 billion, according to research firm, International Data Corp. Even so, that $25.5 billion represents only 7% of all U.S. advertising.

CBS's online empire will be vast. CNET is the 10th most visited Internet site in terms of global unique users and ranks 17th in unique U.S. users. CBS will add CNET's Web sites such as BNET (a business news and information site), GameSpot, News.com, TV.com and MP3.com to its own online operations CBS.com, CBSNews.com, and CBSSports.com. "By acquiring CNET, CBS will more than double Internet revenue and [ad] inventory space," said Frederick Moran, an analyst with the Stanford Group. "CNET also brings a dedicated online sales force and online advertising technology to CBS."

However, the CNET acquisition doesn't address CBS's oft-discussed Achilles Heel. CBS is more vulnerable to an advertising downturn than any of its peers in the industry: 72% of the company's revenue last year was derived from ad dollars, compared to 44% for News Corp., 35% for Viacom, 23% for Disney and 19% for Time-Warner. Although online advertising is expected to grow this year by 20%, companies who derive greater portions of their income from subscriptions generally fare better in a slowing economy.

Some observers are concerned that CBS, which offered a 45% premium to CNET's Wednesday closing price of $7.95 per share, is paying too much for its new Internet baby. Doug Creutz, an analyst with Cowen and Company, put it delicately Thursday morning in a communication with clients, when he called the acquisition "value-dilutive".

Creutz doesn't believe that the synergies CBS has outlined thus far merit the high acquisition price the company will pay. "One of our concerns about CBS has been that management might pursue expensive acquisitions to offset concerns about secular trends in the company's core broadcast television and radio businesses," Creutz said. "The CNET deal underlines this concern." Creutz reaffirmed his "underperform" rating on CBS shares.

Citigroup analyst Jason Bazinet is equally nonplussed. He noted in a message sent to investors Thursday morning that CBS is clearly trying to build a formidable presence on the Web with the addition of an online content company that commands ad rates "well above rivals". However, Bazinet observed, "the key CBS challenge will be sustaining premium [ad rates]." The Citigroup analyst reiterated his "hold" rating on CBS shares. "Merger and acquisition risk and sluggish ad growth continue to keep us on the sidelines," he wrote.

Around midday Thursday, CBS (CBS, Fortune 500) shares had fallen 2.9% to $24.09, while CNET (CNET) shares had risen more than 43% to $11.39. The acquisition is expected to close sometime this summer.