Startup stampede; A frenzied pace of investors raining money.

Byline: Michael J. de la Merced and Mike Isaac

What a difference a year makes.

Less than 12 months after investors valued Snapchat, the red-hot messaging app, at about $10 billion, the startup is again in the market for money -- and poised to nearly double that valuation.

A range of other popular startups are also poised to propel their net worths to similar multibillion-dollar heights, including virtual scrapbooking service Pinterest and ride-hailing app Lyft. Uber, Lyft's top competitor, has raised more than $3 billion in the past year and has an eye-popping valuation of $40 billion.

Giant sums of money and sky-high valuations are nothing new in the technology industry. But the latest burst of activity has put on clear display the frenzied pace of investors, who are eager to catch the next blockbuster company like Facebook. The action is also again spurring talk that overeager investors are poised to relive the dot-com boom and bust at the turn of the century, when overinflated startups led to a quick and painful downturn.

For investors, the hunt is for the next proverbial so-called unicorn, a nascent business worth $1 billion or more -- on paper, at least.

Just last year, 38 privately held companies backed by venture capital joined the billion-dollar club, putting the membership of that group at 54, according to data firm CB Insights. Digi-Capital, a mobile Internet advisory firm, estimates that the total value of startups worth $1 billion or more increased $28 billion in just the last quarter of 2014.

"The grand experiment that we are running right now is: Can you cram hundreds of millions of dollars into 80 or 90 different private companies and have it end up well?'' said Bill Gurley, a partner at venture capital firm Benchmark who is also an investor in, and one of the most vocal proponents of, Uber.

He added, "For some, I think it will end badly.''

Billion-dollar companies were once considered rare. But they are quickly becoming more commonplace. Case in point: Slack, the workplace collaboration startup, hit the billion-dollar valuation mark just eight months after introducing its service. And at $46 billion, Xiaomi, the Chinese smartphone giant that started just five years ago, is the most richly valued private tech company in the world.

Even in recent years, some of the highfliers have landed hard. Fab, an online retailer once valued at close to $1 billion, is now reportedly close to being sold for less than $20 million.

Yet the...