Ruth Calvo, on eschaton and Firedoglake, has been rafting on the Rio Grande, with Mexico on one side and the USA on the other. A glance at the (beautiful) pictures suggests the absurdity of sealing the border.

http://my.firedoglake.com/ruthcalvo/2010/11/05/fending-off-those-illegals/

Ruth offers yet another demonstration of humanity's borders as silly pretensions, in a world larger than we are. Then there are the borders in, say, Europe, changing by the decade against shifting marriages, alliances, wars; even signature nation states like Germany and Italy of comparatively recent origin. And in Africa, current national borders were generally imposed by ignorant, powerful imperialists willy-nilly, for their own purposes, on ancient lands whose ethnicity, religious identity, linguistic groupings and mutual history had nothing to do with them.

All those idiots who want to 'take back their country'--the very wording suggests that it isn't everybody's country, that they're exceptionally entitled to it to the exclusion of others--want tighter borders around their gated communities, their churches, their towns, their states, their country, sealing them all hermetically, canning them in Mason jars, proof against change, so they can be stored in their fallout shelters in preparation for a sociological apocalypse. Won't work, that.