If any one of these 3 things happen, the tech boom could end immediately

Whether you want to call it a bubble or not, the tech industry is booming. At last count there were 114 privately-held companies with valuations of $1 billion or more -- often called unicorns. Some, such as Uber and Airbnb, are worth tens of billions of dollars.  For the tech industry, these are heady times. But economies and industries usually move in cycles. At some point the party has to end.  We polled several tech industry insiders and investors to find out the biggest risks that they se...