Indeed they can’t. Among the crop of companies in the IPO pipeline—likely to top 100 by the end of the first quarter, assuming that you consider three-year-old IPO filings to still be viable—there’s no single “must own” company that has the potential to hold the IPO window open for those that follow it the way that a Netscape, eBay, Yahoo, and Amazon once did, or build up the same kind of buzz about IPOs that Google’s debut commanded.

“There haven’t been any iconic IPOs so far in 2010 that pundits can seize on and talk about,” says Cummings. “The few that are out there have become disproportionately important,” even though in a more "normal" IPO environment their significance would be less.

For instance, the media briefly referred to QuinStreet’s deal as a “beacon of hope” for the venture-backed IPO companies, only to quickly drop that reference when the deal was underwhelming. Now, some market participants point to Silver Spring Networks, a big player in the burgeoning “smart grid” power-management industry (part of the ongoing effort to reduce energy consumption and make it “greener”) as the next candidate for this role. The company has backing from top Silicon Valley venture firms like Foundation Capital and Kleiner Perkins Caufield & Byers and will carry Morgan Stanley’s seal of approval as underwriter.

But this IPO market is one in which nothing can be taken for granted, says Ritter. Even the success of a deal involving a company in one of the market’s hottest emerging industries, supported by top venture capitalists and investment bankers, can’t be seen as a sign of good times. “There are just fewer young companies that are succeeding in going public,” Ritter says. “That’s a big structural change, and I don’t know that it’s healthy for our economy. I would argue that just as there were probably too many IPOs in the 1980s, we are going to continue to see too few today.”

The classic IPO candidate—the small startup—faces a lot more hurdles today than it might have even a decade ago. In the wake of the credit crisis and the market meltdown of 2008, investors today are hyperalert to liquidity risk; they’d rather put their money into a big IPO of a mature business or a deal like last year’s IPO of infant formula manufacturer Mead Johnson Inc., spun off by Bristol-Myers Squibb.

Keith Lister, who runs the syndicate desk at Thomas Weisel Partners, says that startups—those already in the IPO pipeline and the large number expected to file for IPOs in the next two or three months—are the companies that historically have earned the biggest returns. “These are all businesses that have weathered the storm of 2008 to 2009 with flat to slightly positive revenue growth,” he points out.

But these days a startup company will have to compete with a new kind of IPO that has become a powerful force over the last decade: that of private equity-backed companies, which historically have been a fraction of the number of completed IPOs and yet which have outnumbered the number of “classic” venture-backed IPOs in three of the last five years. Five of the dozen IPOs completed so far this year were backed by private equity firms.

True, buyout-backed IPOs have struggled as well, with Graham Packaging (a plastics company owned by Blackstone Group) having to settle for only $167 million in IPO proceeds, less than half of what it had hoped to raise. Investors aren’t going to pay up for a business, however stable, that is lumbered with too much debt, notes one banker. On the other hand, big private equity firms are just as keen as their venture capital counterparts to use the IPO market to find a way to sell off some of the companies they acquired during the buyout binge of the last decade and return capital and any profits to their limited partners.

Ultimately, investors will have to decide what scares them most. Are they nervous about sitting around too long in ultraconservative and low-yielding investments? Or worried more about the prospect of snapping up stock in a hot new startup that stalls or flounders? Or does the chance that they’ll pay too high a price for a company that is going public with a well-regarded brand name but a debt load that it struggles to service worry them most?

Ritter’s data suggests that historically, at least, IPOs with some kind of backing—whether from venture capital or private equity funds—have fared better than deals without such a financing history. But it also shows that non-buyout fund-backed IPO candidates have performed better, returning an average of 40.1 percent in the three years following the IPO, compared with 36.8 percent for a buyout-backed IPO. “It remains to be seen what today’s investors value most and what risks they see as more important,” Ritter says. “That is what will determine the fate of startup companies trying to tap the IPO market.”

For now, however, about the only kind of new stock issue that most investors feel at ease with is the type that is sold by companies that are already public faces and known to the market.

“The capital is there and available, but mostly for companies with established records as public companies,” says Cummings. “Those are the safe havens in the equity market.” IPO volumes may have slipped, but not the number or size of follow-on or secondary issues by already-public businesses. Ever since the stock market hit its post-crash bottom almost exactly a year ago, those secondary sales have had a kind of success that a startup company or other IPO candidate can only dream of.

“Success begets success,” says Cummings. Maybe it’s time for IPO underwriters to hop on Friendfinder.com and post an ad seeking the next generation of Netscapes and Googles?