Diller is forthright in saying that his strategy for IAC over the years has been guided as much by curiosity as by anything that might constitute an actual business plan. This is a novel approach for the leader of a publicly traded company. The only others who practice it so openly are Larry Page and Sergey Brin, at Google. But their curiosity has been justified by wealth creation to the tune of $170 billion, a far cry from Diller’s own. Yet as George Mair wrote in his 1997 book, The Barry Diller Story, “Diller is one of the few executives in the entertainment business who can raise billions of dollars with just his name and vision as collateral.”

IAC’s roots trace back to 1995, when Diller, recently fired from home-shopping network QVC, hooked up with Malone at a broadcasting company called Silver King, which the two later merged with the Home Shopping Network, QVC’s main rival. From there, HSN embarked on a dizzying series of acquisitions, shifting its focus from shopping to entertainment and eventually to the internet. A number of Diller’s moves were particularly well-timed. In 1997, he bought the USA Network and a passel of other entertainment properties from Seagram, sold them at a profit to Vivendi, and secured himself a $275 million gig as a part-time executive in the process. In doing so, he also extracted a concession from Malone about his future autonomy that proved to be his ace in the hole in March.

His early Web moves were prescient. Deals of note include nabbing 50 percent of Ticketmaster from Microsoft co-founder Paul Allen in 1997 in exchange for 17 percent of HSN, snatching up Hotels.com and Match.com in 1999, and paying $1.5 billion for 51 percent of travel website Expedia in 2002. In mid-2003, investors were cheering him on from the sidelines, and the market valued IAC at about $60 billion.

But since then, Diller has seemed less a visionary and more a spastic dealmaker. He has missed some big acquisition opportunities, including ­MySpace, which was snapped up by News Corp. for a fraction of what it’s worth today, and ticket broker StubHub, which would have folded in nicely with Ticketmaster. Instead, Diller went in for questionable deals, such as the 2005 purchase of the old-media catalog company Cornerstone Brands, an acquisition he has described as a mistake, and the 2006 purchase of ShoeBuy.com, a distant also-ran behind market leader Zappos.com.

His once-vaunted theme of interactivity, which had a sexy sheen 10 years ago, now seems stodgy, akin to making “We sell things” your corporate mantra.

His costliest misstep has been holding onto mortgage middleman LendingTree, which he purchased for $726 million in 2003. Diller could have made a fortune for IAC if he had sold LendingTree at the height of the housing boom in 2005, which is the kind of move you’d expect a master dealmaker to pull off. Instead, he held on, and he now admits that the unit is worth “vastly less” than what he paid for it. IAC wrote down the value of LendingTree by $475.7 million in 2007. Expect more where that came from.

While Diller may be perceived as a titan, Cowen & Co. analyst Jim Friedland says the value he’s created in the recent past has been puny. “Give or take, the return on invested capital has roughly been between 4 and 5 percent over the past several years,” Friedland says, “which is about the same return you could have received if you’d bought a Treasury bond.” If IAC’s cost of capital is 10 percent, which is Friedland’s estimate, Diller and his curiosity have been destroying value to the tune of about 5 percent a year since 2004.

Of course, the most relevant measure of the value of a publicly traded company is the price of its stock. From December 31, 2004, through April 25 of this year, IAC stock was down 63.3 percent, while the Nasdaq composite index had gained 11.4 percent. The company has pretty much been going through one wrenching transition after another for the past several years, and the stock has performed poorly over much of that time. The synergy that Diller so desperately sought among the more than 60 individual brands IAC owns has failed to materialize in any meaningful fashion. Diller nevertheless points out that IAC stock is up 237 percent since the company’s creation in 1995, even as the S&P 500 has risen only 138 percent.

"The best asset they have is Diller, who is running an internet company the same way you'd run a media conglomerate," says senior analyst Jeffrey Lindsay of Sanford Bernstein. “He had a good run for a few years, when the assets were firing on all cylinders. The mark of a very good business, though, is how well it can ride out a downturn. At this minute, it doesn’t seem to be doing it that well.”

The Gehry-designed IAC building is a monument to Diller himself. It’s a flashy, shape-shifting wonder at the edge of New York’s hottest neighborhood. Getting to Diller starts with walking through a lobby that seems designed for a catered cocktail party. A massive video screen showing the traffic on various IAC websites sits behind the reception desk.