Technology, regulation and growing competitors are chipping away at Telmex, the cornerstone of Slim's telecommunications holdings, and once-frantic sales growth at his America Movil wireless operator is tapering off.
Slim, who acquired creaking telephone monopoly Telmex from the government in 1990, shook it up and expanded it across Latin America, is increasingly challenged by media giant Televisa and smaller cable television operators.
In a sign of tougher times for Slim, Telmex, once the crown jewel of his business domain, was the only stock in Mexico's IPC benchmark index to lose ground last year, falling nearly 25 percent as investors bet future profits will shrink.
"He has a collection of crowns and a collection of jewels, said telecommunications consultant Ernesto Piedras. "But any company has its business cycle. His most dynamic phase has passed."
But 69-year-old Slim is still a massive force to be reckoned with in Latin America with his regional fixed-line operator Telmex Internacional, upscale Mexican retail stores, Inbursa bank and infrastructure developers.
NECK AND NECK
After markets bounced back last year following the global credit crisis, Slim is likely worth $59 billion, putting him in contention with Microsoft Corp founder Bill Gates for status as the world's richest man, according to Sentido Comun financial website editor Eduardo Garcia, a respected Mexican wealth tracker.
In Mexico, where key industries are often heavily dominated by one or two powerful families, companies controlled by Slim, a former trader, account for more than a third of the capitalization on the stock exchange.
With more than 80 percent market share, Telmex remains by far Mexico's largest fixed-line telephone and Internet operator, although revenue is steadily declining as it freezes prices for a 10th straight year to stem customer losses.
Despite creating thousands of jobs and billions of dollars in wealth, Slim has become a magnet for criticism of powerful companies and monopolies in Mexico.
Critics say long-held strangleholds by Slim's telecom companies, broadcaster Televisa and cement maker Cemex in their industries have held back economic growth by making it difficult for aspiring entrepreneurs to compete.
Experts say Slim's rates are expensive, but rivals including Telefonica, and cable operator Megacable are slowly making headway, and prices and services are improving. Technology has allowed cable companies to move into Internet and phone services, long dominated by Slim.
"Before, if you wanted a (new) line it took years, there was just one option. Now, you can choose," said Yadira Navarro, an accountant at a retail cement distributor in Mexico City.
President Felipe Calderon has vowed to improve competition in industries dominated by big companies, but progress has been very slow.
All the same, regulators have refused to let Telmex offer television services, giving cable operators an edge.
Mexico's anti-trust watchdog is probing alleged price collusion in the cement industry by Cemex -- a major Mexican company not owned by Slim -- but penalties for monopolistic practices are paltry and rarely applied.
Slim denies that his companies have stifled competition in the telecommunications industry and says he has helped make Mexico's economy stronger.
"I'm very proud," Slim told foreign journalists at a luncheon in 2008. "It's perverse to think poor countries should not have big companies."
As part of the effort to stir up competition, Mexico is auctioning radio frequencies to let mobile telephone operators expand their services. While America Movil will probably acquire some bandwidth, rival Telefonica is likely to be the big winner.
Telefonica, a distant No. 2 in Mexico's cellphone industry, lacks third-generation coverage needed to offer Internet services in the lucrative Mexico City region and has been waiting for years to acquire more frequencies.
Once-limp rivalry in Latin America's telecom industry has firmed in recent years but has been hard to detect as America Movil and other players took on new customers in an under-served market.
"Now that there's not a lot of growth, its easier and easier to spot the competition," Coello said.
In Colombia, regulators recently put limits on how much America Movil can charge for calls to numbers outside of its network. Mexican regulators have imposed ceilings on what Slim's telephone companies can charge other carriers to connect calls through their networks.
Plans are also under way for Mexico to create a new cross-country telecom industry backbone, creating an alternative to Telmex's infrastructure, upon which operators currently depend, increasing competition more.
America Movil may have added 5.6 million new lines in the fourth quarter, Coello predicted. While that is sizable number of new clients, it would still be down 45 percent year over year, the company's weakest fourth-quarter expansion in seven years.
While Telmex's fixed-line business shrinks and its Internet unit faces more competition, telecommunications in Latin America are still seen outperforming other industries.
"This sector has to potential to grow several times faster than the economy," Piedras said. "It will continue to be a very safe business because people always want more rather than less telecommunications."
(Reporting by Noel Randewich, editing by Maureen Bavdek)