Why exactly is that mega-brand mergers never quite live up to their grandiose expectations?

The question has been asked hundreds of times in the last decade, but is more relevant than ever as woes deepen for Oprah Winfrey’s ill-fated cable venture. In a landscape littered with the carcasses of discarded corporate names like Hewlett Packard-Compaq, Citigroup, and AOL-Time Warner (the forerunner to the now equally-troubled AOL-Huffington Post marriage), Discovery Communications’ conversion of its Health channel into the Oprah Winfrey Network (OWN) is hemorrhaging cash. Alas, media watchers are already warning that the splashy joint project with the former queen of daytime television stands a real possibility of being put out to pasture within a year.

At first blush, the biggest loser in the spluttering merger appears to be Discovery. When the network announced its first quarter earnings this week, its bottom-line – excluding OWN – was a picture of financial health that investors would otherwise have welcomed. Sadly, the fledgling channel’s modest subscriber growth is being dwarfed by its massive financial losses, news that sent its stock reeling. According to Bloomberg News, the network’s cumulative losses may have exceeded $300 million since it first started.

Although Discovery CEO David Zaslav recently predicted OWN would break even by next year, financial realities have a bad habit of undermining the most optimistic projections. An accumulating pool of red ink — and the growing chorus of bad press — tells a starkly different story.

For sure, not all the news is this grim. OWN recently unveiled a slate of new programming, and has aggressively slashed costs – including Rosie O’Donnell’s talk show, which earned anemic ratings. Oprah’s Next Chapter, Winfrey’s news-maker interview show, debuted to record ratings in January, and scored a major coup with a show featuring the late Whitney Houston’s family shortly after her untimely demise. It underscores what some observers insist is the network’s ace-in-the-hole: Winfrey herself. Despite giving up her talk show, the Cult of Oprah retains a passionate following. The self-made media queen’s estimable personal narrative resonates with huge swaths of the population, making her name alone a potent draw for advertisers and viewers.

Yet it goes without saying that Oprah’s second act hasn’t unfolded the way anyone expected when it was announced amid much fanfare in January 2011. The alchemy normally associated with her personal brand seems to have deserted her with OWN. Winfrey’s personal stake in the venture is limited – one media analyst recently pegged the losses to her production company Harpo Studios at $143 million. While that sum is disputed, it still represents a mere fraction of her estimated $2.7 billion personal worth.

Some of the problems dogging OWN are rooted in the rough-and-tumble world of corporate media, which is in a state of perpetual evolution beyond Winfrey’s ability to control.

Oprah’s biggest issue appears to be that she was a late entrant to the fiercely competitive contest for female viewers. In a roost ruled by women’s networks like Lifetime and WE Television, OWN was always likely to have an uphill climb — especially in a field that tends to cannibalize upstarts, regardless of how big a name is behind it. And as far as troubled corporate mergers go, Winfrey is in fairly distinguished company among female entrepreneurs. Arianna Huffington’s link-up with AOL has become a crash-course in humility for a woman once feted by cultural elites. Meanwhile, Carly Fiorina’s reputation has yet to fully recover from the battering it took after she forced through a star-crossed marriage between Hewlett-Packard and Compaq.

All of which means the potential failure of OWN could represent a big black eye to Winfrey’s hard-earned cachet. Winfrey is certainly no stranger to failure: the accolades that followed her movie and television roles were no help to her movie adaptation of Beloved, which crashed and burned upon lift-off from the box-office. Meanwhile, her South African girls academy — a noble endeavor — was initially plagued by scandal before it triumphantly graduated its first class in January.

Still, being closely linked to a network going under could be a setback on a vastly different scale. Winfrey would still have her vast fortune and long record of accomplishments to fall back on. Yet her storied reputation could be sullied if she becomes known as the woman who helped sink Discovery Communications – or gets ignominiously shown the door if it doesn’t work out, (as Disney once did to its controversial former chief executive, Michael Eisner).

The media queen’s crown may be tarnished, but, at least for the moment, it still has all its jewels. Oprah herself recently called OWN the “climb of her life,” and she’s absolutely right. One thing appears certain: she has a limited window of time to recover her poise, or she will end up crashing down upon the craggy rocks that lie at the base of that mountain.