As cars require more software, the line between vehicle and computer is rapidly blurring. Apple, Google and Blackberry all offer in-vehicle software, while the push for self-driving cars is pitting long-time automakers against tech companies.

Car brands could be in trouble on two fronts: losing the race to offer autonomous vehicles and becoming shells for software similar to the phone handset industry.

While Google's self-driving prototype exemplifies the potential threat from Silicon Valley, Daimler CEO Dieter Zetsche had some reassuring words this week.

The Mountain View, Calif.-based tech giant is unlikely to focus on mass production for cars; instead, its self-driving auto program aims to further innovation, Zetsche said.

"Google and the likes want to get involved, I don't think in the first place to build vehicles," said Zetsche, as quoted by Reuters.

"We have to understand that, and then to find our roles, to which extent they are complementary, to which extent we become dependent, to which extent we are competitors," he added.

Zetsche may not be worried yet, but some of the auto industry's strong players, analysts and enthusiasts have had quotes that are far less reassuring.

1. Ford CEO Mark Fields: "There are others who we never thought five years ago would be competitors for us ... Guess what, they are looking at our industry, not taking anything for granted, they are questioning tradition and they are knocking down walls. I want to make sure Ford doesn't end up like the handset business."

2. Morgan Stanley Analyst Adam Jonas: "It's almost an unfair advantage. As software goes from 10 percent of the value of the car to 60 over 10 years, that disadvantage [for traditional carmakers] will intensify."

3. Designer Joe Nuxoll: "You try to design [the Tesla display screen] so that it requires not a whole lot of thinking. It's more like an iPhone than a Ford."

4. Lord Charles March: "The car companies will become irrelevant ... Cars will just become a house for the software."

5. MIT Scientist Bryan Reimer: "I think the two tech behemoths, Apple and Google, are moving quickly into position. There is a major battle starting to brew over who will take control."

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