Why people keep saying that our economy will plummet if we phase out petroleum?

Question

What are their logic behind this conclusion?

Are they speaking for the oil companies only?

Answer 1

Phasing out petroleum is impossible for USA, period.

If we stop importing oil for a few weeks, there would be a big mess beyond repair. And its not oil companies, its us. WE are so oil dependent that we often fail to realize that its not only gas for our cars, but also its in everything that we use.  

Answer 2

Only OPEC and Oil companies will plummet.

Answer 3

it's too expensive.  the alternative energies cost more