The world is buzzing about Twitter’s role in Iran, but what kind of impact is the news in Iran having on Twitter?

Last week, the world watched with bated breath as tens of thousands of protesters poured into the streets of Tehran in the wake of Iran’s disputed presidential election. Well, it watched for a couple of days, at least—until Iran cracked down on the media. After that, the world tweeted.

Beyond boosting the site’s profile, drawing in new users, and casting Twitter as a diplomatic hero, the events of the past few weeks have had a number of other benefits. For many of those who saw Twitter as little more than a monument to shrinking attention spans and egocentric navel-gazing, the election in Iran established the site as a valuable and credible medium for news. And despite the influx of traffic, Twitter proved itself technically sound, avoiding major technical failures and keeping downtime to a minimum.

What’s the value-added on a global news coup (and some good mojo from the State Department)? Maybe less than one might think.

In a profound demonstration of the power of social networking, surfers searching “Iran election” turned to Twitter more than any other site on the Web last week. Twenty-five percent had never visited the site before. Twitter’s closest runner up, with 14 percent? Google News. By the middle of the week, the total number of election-related Tweets—averaging 10,000 to 50,000 Tweets an hour, and spiking past 220,000 an hour on June 16—had soared past 1 million, according to Mashable.

Twenty million users strong—and $55 million in debt—the micro-blogging site from San Francisco found itself thrust into the public consciousness after the Iranian government banned all foreign media from reporting on the crisis, deporting and arresting those who disobeyed. After that, CNN, BBC, Al-Jazeera, and virtually every network in the world had no choice but to turn to Twitter, reporting breaking news 140 characters at a time. World, meet Twitter.

“The rampant media attention has helped accelerate the growth curve for Twitter in a way I haven’t seen before,” says comScore’s Andrew Lipman. “Over a course of just a couple of months, Twitter went from 2 million visitors to 4 million, to 9 million, to 17 million. That is literally unprecedented growth for a site that size.”

“Before, the news was all about record growth and Tweeting celebrities,” says Heather Dougherty of Hitwise. “But the election in Iran has excited people because it allows them to talk about Twitter in a more meaningful way.”

There is perhaps no better testament to the profound role Twitter now plays in social and political developments the world over than the news that the U.S. State Department reportedly contacted the company at the height of last week’s protests, requesting that it delay scheduled site maintenance in order to keep open a valuable line of communication in the face of the media blackout. Kudos from the State Department? Talk about one hell of a merit badge.

Indeed, the biggest names in tech have all been haggling over the question of Twitter’s true value. Apple, Microsoft, and Facebook have reportedly all made passes at the 45-employee company in the past year, each to no avail. Twitter even turned down a $500 million offer from Facebook in late 2008, only to turn around and accept a loan from venture capital firm IVC in January, valuing the site at half Facebook’s earlier offer. Such is the spooky math of social networking, where nothing is set in stone. Except, perhaps, Stone. Appearing on an episode of The View, the site’s recalcitrant founder, Biz Stone, declared once and for all, “We’re not for sale.”

While we’d be the last to accuse Stone of lying to Barbara Walters, the founder’s unwillingness to sell hasn’t stopped casual observers from doing a bit of spreadsheet speculation. In May, PaidContent.org drew up a valuation model for Twitter, comparing it alongside “user-based multiples from sales of other low-revenue Web sites”—like YouTube, MySpace, and Bebo. According to its math, Twitter rang in between $304 million and $665 million.

TechCrunch.com joined the T-party less than a month later, applying its own analytical formula to the great Twitter teaser. Published on June 5, just days before the election in Iran, the site’s second annual Social Network Valuation Model used prior valuations of other social-networking sites—like Facebook ($10 billion) and Bebo ($850 million)—as a baseline, then factored in audience size and average online spending per capita on a country-by-country basis. This time, Twitter’s value landed somewhere between $671 million and $1.7 billion.

In light of the fact that both estimates were made in the immediate weeks leading up to the election in Iran, we couldn’t help but ask ourselves: What about now? What’s the value-added on a global news coup (and some good mojo from the State Department)? 2x? 3x?

Maybe less than one might think.

Consider PaidContent.org’s volume-equals-value model. While simple and appealing, the math quickly falls apart in the face of Twitter’s much-maligned user-retention rates. Notoriously fickle, six of 10 Twitter users in one Nielsen study published in April failed to return to the site even once after signing up.

And TechCrunch? We contacted Daniel Romero, the man who crunched the numbers. While he acknowledges Twitter’s ubiquity is growing—nodding to how networks like CNN and ESPN have embraced the site as a source for breaking news and audience engagement—he balked at the notion of rerunning the valuation model to factor in recent events. “Overall, I think the coverage will allow Twitter to continue to grow its user base while at the same time cementing itself at the forefront of movements like citizen journalism and crowd-sourcing,” he said. “[But] the surge in traffic from Iran would have hardly any effect on the valuation as it is mostly in non-U.S. markets, where advertising spending is low.”

In the midst of a global recession, perhaps it should come as no surprise that bold headlines and promising trendlines can’t trump bottom lines down on Wall Street. Of course, this isn’t to say analysts are pessimistic about Twitter’s future. In fact, while media spotlight may not be adding to Twitter’s immediate value, it has done wonders for investors’, marketers’, and spammers’ enterprising ingenuity. Creative suggestions for how Twitter might capitalize on its growing popularity abound—selling keywords in real-time search, location-based ads, corporate accounts, brand tie-ins, and even matching and selling followers to the highest bidder.

Twitter CEO Evan Williams even had to publicly chastise one of his own VC partners this past Monday, after the investor revealed to The New York Times that Twitter would soon be generating sponsored product recommendations in the form of auto-replies to users’ tweets. “These are not in the least bit concrete plans of the company,” Evans later told The Business Insider. Fair enough. With millions of new users flocking to the site each month, the only thing set in stone (or concrete, if you will) is that Twitter is getting ready to cash in.