Scaling New Heights
Join Date: Apr 2007
Location: Hinton, Alberta, .
To get back on topic and answer the question of the OP I did a few back when the project first started. It was an interesting use of the technology and also a sampling of geographic locations around the world. There are some very interesting visit reports listed on the site.
Participants were not limited to hikers with handheld GPS receivers. There are a series of visits by the captain of a freighter on his ship along the shores of both sides of the Atlantic (confluences are limited to intersections of lat & long within sight of land). He also visited at least one inland in Russia at a time when a foreigner (or anybody) with a GPS would have had a hard time explaining themselves to the authorities.
While it's not stated on the website most participants would expended a lot of effort to be the first to visit a confluence and lost interest if they were not.
The Canadian coordinator is a sometimes poster in these forums.