You know it's a bubble when venture capitalists roam the corridors of South of Market office buildings. Pui-Wing Tam, the Wall Street Journal reporter detained by Marc Benioff's construction crew when she tried to peek at his Hawaii getaway, gets a warmer welcome at 625 Second Street, the building occupied by also-ran internet portal, Looksmart — and by a host of new web startups. Key bubble indicators: tenants have to be invited into the building; it's home to one of the self-styled Young Guns, gregarious Yalie, Rob Pazornik of Licketyship; and then there's this:

Mr. Simonelli, LookSmart's 43-year-old CFO, says the start-ups have given the building new energy — but not him. "The other day, the LookSmart general counsel and I were talking on the third floor," he says. "A Silicon Valley venture capitalist popped by and wanted to know which start-up we were. I had to tell him that we were the old fuddy-duddy Internet company."

In San Francisco, Bust Becomes Boom At 625 Second St. [Wall Street Journal]