I love the banana argument due to one simple fact:
Bananas in the form referred to by Cameron were in fact intelligently designed -- by a long history of botanists and farmers crossbreeding
the seeds out of the banana fruit. They are in current form today essentially cloned (much like potatoes are.)
So yes, they are evidence of intelligent design. Of course, it's man's very earthly and science-based intelligent design.
ETA:
Some sources for the claims above:
http://www.gmo-compass.org/eng/groc...netic_engineering_against_fungal_disease.html
http://www.commondreams.org/views03/0719-02.htm
from the above link:
The banana's main problem is that it has become sterile and seedless as a result of 10,000 years of selective breeding. It has, over time, become a plant with unvarying genetic sameness. The genetic diversity needed to cope with environmental stresses, such as diseases and crop pests, has long ago been bred out of the banana. Consequently, the banana plantations of the world are completely vulnerable to devastating environmental pressures.
http://wwww.cirad.fr/presentation/programmes/biotrop/resultats/biositecirad/transfo/bananatg.htm
http://www.tytyga.com/publication/The+History+and+Evolution+of+Banana+Tree+Hybrids
from the above link:
Those first bananas that people knew in antiquity were not sweet like the bananas we know today, but were cooking bananas or plantain bananas with a starchy taste and composition. The bright yellow bananas that we know today were discovered as a mutation from the plantain banana by a Jamaican, Jean Francois Poujot, in the year 1836. He found this hybrid mutation growing in his banana tree plantation with a sweet flavor and a yellow color—instead of green or red, and not requiring cooking like the plantain banana. The rapid establishment of this new exotic fruit was welcomed worldwide, and it was massively grown for world markets.
All Cameron shows in arguing the Banana as evidence of god is his complete lack of knowledge about the history of breeding bananas for the world's food markets.