To make Elon Musk giggle, bring up Uber and autonomous cars

I think it just hit him where he most likes it.

He is succsfully disrupting the automotive industry.

Now he gave him an idea to disrupt a hugely profitable industry even before it's fully established. (ride-sharing/Uber)

The idea tingled his southern regions.

Autonomous cars are an existential threat to Uber. It doesn't make sense for a manufacturer like Tesla or Google to leave money on the table like that. Hence Musk's reticence on commenting.