By VERNE KOPYTOFF, San Francisco Chronicle

No, they're not Hollywood A-listers like Oprah or Ashton Kutcher, who have collected more than a million fans on the micro-blogging service.

Rather, they're three relative unknowns from Northern California who, through tireless hobnobbing, nonstop posting and, in one case, luck, have joined a rare club: Twitter's citizen celebrities.

You can orbit the moon and take narrated video tours of the Apollo lunar landings as part of Google Inc.'s latest mission into space.
The Internet company enhanced its 3-D mapping service this week with imagery of the moon, coinciding with the 40th anniversary of Neil Armstrong's giant step for mankind.

When he can, Jonathan Fleming uses PayPal instead of a credit card to shop online, whether to buy a television from Amazon.com or tickets from Southwest Airlines.

Emboldened by a few glasses of wine one Saturday night, Tara Hunt ranted on Twitter about her frustrations with San Francisco's dating scene. She soon regretted it.
At work a couple of days later, her venting was topic No. 1 in the boardroom at Intuit, where Hunt works in marketing. Her colleagues had read the message and, to her embarrassment, chimed in about her love life.

A saying repeated over and over in the technology industry is that the best time to build a company is during a downturn.
Many entrepreneurs are testing the theory by forming their startups this year, when many more established companies are cutting jobs and, in some cases, shutting down.
Optimistic? Definitely.
Foolish? Only time will tell.

Few endorsements can match one by Yahoo CEO Carol Bartz earlier this month when she surprisingly declared that a competitor, not her own company, was the best source of driving directions.
"I don't use Yahoo Maps, I use Google Maps," she divulged at an investor conference. "I'm just telling you."

Increasingly, Facebook and Twitter are overlapping, setting the stage for one of the biggest Silicon Valley rivalries over the next few years.
Both companies want to play a major role in how people communicate online, a potentially lucrative business but one that is hardly settled given the ever-shifting landscape.

In his daily search for work, Dan Dalton scours nearly a dozen online job sites for openings.

Nine years ago this week, Internet mania peaked when the Nasdaq reached an all-time high of 5,132.52.
But the heady days of initial public offerings, whimsical ad campaigns and big spending would soon end. Web sites once heralded as the wave of the future disappeared. Layoffs, bankruptcies and unhappy investors abounded.

Already one of Silicon Valley's hottest startups, Twitter -- a cross between instant messaging and blogging -- has won legions of converts and has emerged as a cultural phenomenon.
But as the company grows, it faces a new challenge: turning its popularity into a business.