In the technology world, no question comes up more frequently these days than "Are we in a bubble?" And while it's not up to us at CNBC to answer that question, we do sometimes happen upon little nuggets—data, anecdotes, tweets and the occasional wild party that can possibly help others make their own assessments. When we do, we'll share them in an occasional column we're calling "Bubble watch?"
From a macroeconomic level, things look frothy, to say the least. In San Francisco, median home prices recently topped $1 million and prices in many parts of the Bay Area have exceeded their housing bubble highs from last decade. Commercial rent is soaring and employment rates in San Francisco are at a record.
Data on the financing side is no less dramatic. Venture funds are raising the most capital in eight years and, along with private-equity firms and hedge funds, investing more in start-ups than at any point since 2001. It was once rare to find a private tech company valued at $1 billion–they're often called unicorns. They now number in the dozens, with a select few having reached $10 billion.
And then there's Yo. An app that lets you send a one-word message to your friend takes the tech world by storm and goes viral even as many people in the know wonder if it's a joke. Humorous or not, the messaging battle is real. Snapchat turned down a $3 billion offer from Facebook, but WhatsApp couldn't say no when the social network upped the payday to $19 billion.
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Fortune magazine's Adam Lashinsky wrote in May that he'd received a call about an opportunity to buy "friends and family" shares in an upcoming initial public offering. He declined, "but as I hung up the phone, I realized that I finally had tangible confirmation that we are squarely in the middle of a tech-company bubble," he wrote.
Nobody knows for sure when the music will stop and how bad the damage will be when it does. But one thing is evident: the noise is getting louder.
—By CNBC's Ari Levy.