As America deals with fallout from bad loans, the major networks — flush with a surge of tune-in for big events — must again contemplate the value of “borrowed audience.”

Shakespeare warned about the perils of borrowing, but that’s essentially what the networks are doing every time they attract an oversized audience that really isn’t predisposed to return for primetime series — especially men who watch football and the Olympics and youths who show up for events like the Grammys.

For the networks, part of the thrill is just drawing massive crowds like they once used to garner — a rare point upon which even CBS’ Leslie Moonves and NBC’s Jeff Zucker can find common ground. During the 2008 Olympics, Zucker suggested that the network’s inflated ratings prove “the pipes still work,” while Moonves told the Associated Press of the recent record-setting Super Bowl, “For anyone who wants to write that broadcasting is dead, 106 million people watched this program. You can’t find that anywhere else.”

Clearly, audiences are showing up in growing numbers again for such marquee properties — fueled in part, some suspect, by the downturn in the economy, and perhaps even a desire for communal viewing experiences. This year’s uptick for award shows, including the Grammys and the Golden Globes, along with major sports bodes well not just for the Winter Olympics but for the Oscars as well.

Still, a cynic might ask, to what end in the bigger picture? And what sort of premium do these showcases truly merit if most of the audience that tunes in scatters — with little thought of returning — as soon as the clock hits zero or the last award is presented?

Given that negotiations for the 2014 and 2016 Olympics loom — along with a new contract for the Emmys — this is far from just an academic exercise. Moreover, pro football’s owners and players union are about to go to war over compensation, which will be tethered in part to whether the NFL can count on TV money (from which the owners currently pocket $3.7 billion annually) to offset their self-described financial woes.

If one began designing official uniforms for these kind of ratings platforms, they would come with broad shoulders and extremely short coattails. Other than the “Kumbaya” moment of seeing millions gather around the TV hearth, the explosion of channels and screens vying for time and attention remain a mighty force against aggregating such large crowds, causing them to disperse faster than ever.

CBS appeared to enjoy a small Super Bowl afterglow, with an influx of viewers for its Monday-night comedies the day after the game. By Tuesday, though, the network’s ratings looked pretty well back to normal.

NBC has already said it will lose $200 million on the Vancouver Olympics, which means all the inevitable promos for “The Marriage Ref,” “Parenthood” and Jay Leno’s return to latenight had better yield some benefits after the torch has been doused. Yet while there’s no precise way to measure the lingering effects, history hasn’t been particularly kind to programs launched on the backs of Olympics and Super Bowls past.

The Peacock’s dominating performance with the 2008 Summer Games ostensibly did little to forestall the assortment of troubles the network has experienced in the intervening 18 months. ABC’s frustration translating “Monday Night Football” ratings into help for the rest of its schedule in part explains why the network let the franchise migrate to sister Disney net, cabler ESPN.

Indeed, Fox’s own trail of tears turning baseball’s World Series into a leadoff hitter for traditional primetime fare — despite being a poor fit, demographically, with the network’s signature programs — is apparently what prompted scheduling guru Preston Beckman to coin the “borrowed audience” phrase.

Given the premature obituaries being written for broadcasting, high-profile reminders of its unrivaled ability to assemble mass audiences do possess psychological value. Nevertheless, the rationale behind paying top dollar for such annual showcases — and the reason networks have often been willing to lose money on them — has always rested upon their perceived potential to bleed beyond the few hours they occupy and assist in launching future hits.

Tallying up borrowed audience might yield the fleeting joy of victory, but that doesn’t amount to much. The real riddle network bookkeepers must decipher is determining what, if anything, that temporary infusion of interest buys them if it fails to yield long-term dividends.