Why Arks?

Some issues that will be important during the early evacuation planning:

• Who is going to be doing the planning?  Obviously, the
  national governments would like it to be them.  Will this be the
  case?
• What is the cheapest way to get humans into space and keep them
  there, alive and sane, given advanced propulsion and energy generation?
• How can we conserve as much of what's important on Earth as
  possible?  And what are our criteria for importance?
• How do we minimize the amount of last-minute assaults on each
  other that some parties (national or otherwise) will undertake?

Some issues that will come into play regardless of intent:

• Pride in humanity's abilities in the face of advanced aliens
• Resistance or stubbornness when being told to evacuate
• Religious issues
• Fear of corruption on the part of the planners, Journeymen, etc.

The working meeting that comes up with the answer of "build Arks" must
make sure that this answer is actually correct for their scenario,
otherwise I need to rethink my story :)