I wrote an implementation of this for this project: http://vimeo.com/uuorld

It's MUCH harder if you want adjacent borders to line up w/o gaps. You have to find all shared verts, run the smoothing algo on them, do the same for the coastlines / islands and then put all the pieces back together. I think 10% of my code was cleaning dirty data (removing duplicate points, detecting and fixing self intersection) 80% of my code was breaking everything up and putting it back together and 10% was the Visvalingam / Whyatt algo.

The biggest time sink was dealing w/ messy data. Between countries, states, counties, zip codes, neighborhoods etc, we hit A LOT of crappy corner cases. If anyone else is endeavoring to do the same, contact me and I can probably save you a week of work.