Every day brings an earnings release, government report or trade-association survey that indicates the worst is behind us. Even news from the long-dormant upper reaches of corporate dealmaking is encouraging. Disney (NYSE: DIS), Dell, Xerox and Cisco (NSDQ: CSCO) – “strategics” in every sense of the word – are all in the midst of billion-dollar acquisitions, and Comcast (NSDQ: CMCSA), GE and Vivendi (EPA: VIV) are seeking to hammer out some kind of megadeal for NBCU. On a smaller scale, Intuit’s $170 million takeout of hot competitor Mint.com and the gravity-defying valuation bestowed on Twitter have energized bankers and entrepreneurs alike.

Still, it’s hard to find a more pessimistic bunch these days than private-equity managers, who are understandably feeling like there’s a dance getting underway and they’re not invited. Private-equity firms and companies they control have largely abandoned the M&A marketplace, forced instead to nurse last year’s over-leveraged and under-performing acquisitions back to health, even as they are shut off from the financing needed to do new deals. Capital IQ reports that the value of PE-backed deals in North America through September of this year dropped to less than 5% of what it reached over the same period in 2007.

Despite the government’s efforts (hopefully not its best efforts), origination windows at many bank and non-bank lenders remain shut except for virtually investment-grade borrowers, and the time needed to assemble syndicates of transaction-friendly lenders has mushroomed from days to weeks or many months, unimaginable two years ago. Bank distaste for risk, moreover, and the consequent return to rigorous underwriting, has turned what used to be the typical deal’s capital structure on its head.  Far more equity is needed to entice those skittish lenders, and only private-equity firms with plenty of dry powder (meaning the ones less dependent on other people’s money) will get deals done (such as the tentative PE-backed buyout of IMS Health).

What’s causing real agita in the PE community, though, may simply be inside knowledge of what’s lurking in fund portfolios. Only a trickle of leveraged loans has come due in the past year compared to what was lent during the boom and will be maturing in the 2012-2014 period (roughly $430 billion, versus about $11 billion in 2010). This suggests, of course, that PE portfolios, media included, are packed with potential trouble, and the only reason we’re not seeing more of it right now is that many of those loans were issued with covenants light as photons. Fund managers are already working overtime to renegotiate and extend terms ahead of this potential tsunami. But without a return to sustained economic growth that allows for rising profits and the ability to pay down debt, a new wave of defaults is likely.

In fact, sickly media companies that under normal circumstances would have already been forced into bankruptcy, removing excess capacity from the system, remain alive – zombie-like – only because they are not in violation of their flimsy bank covenants. Some lenders, moreover, are complicit in keeping these companies afloat because they don’t want to recognize them as non-performers and write them off, potentially triggering their own financial suicide.

So with the true cleanup barely underway, with lenders more risk-averse than ever, and with the economy only slowly regaining its footing, the odds of any return to the freewheeling borrowing that fueled private equity’s joy ride and helped inflate prices in media buyouts is unlikely for several years.

Some argue that the thinning of private-equity buyers will undermine the deal marketplace less and less as the economy gains steam, since healthy strategics always have “above the line” interests that let them extract greater value than a financial buyer and thus allow them to outbid private equity. There is some truth to this. But without PE funds bidding and nudging prices higher, strategics are unlikely to “pay up” with pre-recession regularity.

It’s worth noting, as well, that the outsized rewards enjoyed by private-equity partners over the past decade attracted some of the sharpest minds in business. Many have understood well in advance of in-house corporate strategists and planners the key impact of new technologies and media. And without legacy properties and installed technology bases to protect (and admittedly using other people’s money), private-equity funds often embraced risk where strategics fled. The growth and development of technology in media will be diminished until the PE market rights itself.