IMVU Chief Executive Cary Rosenzweig used to make his living pushing practical products such as Tide, Clorox and QuickBooks Payroll. Now he leads an Internet "virtual world" company where visitors spend actual money for something as seemingly frivolous as a new wardrobe for their digital alter egos and gifts for avatar pals.

Yet IMVU recorded four consecutive quarters of record revenue in 2008, accelerating even as the economy crashed, Rosenzweig says. With the holiday season over, business was expected to slow a bit — but January delivered another uptick, he said. Why? One theory suggests that people with maxed-out credit cards were substituting low-cost shopping sprees in the virtual realm for trips to the mall.

As layoffs mount, Wall Street swoons and consumer confidence plummets, some business executives have become fond of saying, "Flat is the new up." Yet a number of venture capital-backed private companies in greater Silicon Valley appear to be growing stronger in the leaner, meaner economy, sometimes confounding even their own expectations.

"Last quarter, we absolutely believed we would see some negative impact," said Dave Robbins, CEO of BigFix, an Emeryville maker of a centralized computer management system for customers such as Stanford University. "And we had to reforecast our business upward three times."

BigFix, he said, recorded 80 percent growth in 2008.

And Ingres, a Redwood City-based open-source

database company, finished 2008 with its strongest quarter, bringing revenue up 32 percent for the year, according to CEO Roger Burkhardt.

Companies that seem to defy the downsizing economy represent a wide range of industries. They are flexing their muscles in a variety of ways, adding customers, talent, investment capital and in some cases spending profits on acquisitions. Some of the companies are obscure and play in the economic background, and some have high profiles among consumers.

The social-networking site Facebook and professional network LinkedIn continue to assert their leadership status in their respective niches, adding customers and features for the millions of users worldwide. Glam Media, an ad-heavy lifestyle site devoted to women, has grown to 75 million unique visitors per month. While advertising is softening, Facebook and Glam rank as the only privately owned Web sites to rank in comScore's top 10 most used sites in 2008.