Is "Junk" DNA Used to Provide Genetic Memory

[Laurence Fiddick;x2791]

In <graulCoz9Hq.ILx at netcom.com> graul at netcom.com (Rick Graul) writes:

>The purpose of "junk" DNA,
>as I understand it, is to provide a reservoir of elements
>which can be used by the organism for creating new genes.

i'd be interested in any references you might have on the purpose of junk dna.
presumably there is some cost to carrying junk dna, and i somehow find it
hard to believe that natural selection can maintain it for such uncertain 
long term interests--so any refs on this or any other arguments for the 
adaptive value of junk dna would be appreciated.