Described here : http://www.stigmergicsystems.com/
Stigmergy is roughly "communication through leaving cues in the environment" as with chemical trails left by ants.
JohnRobb now using this idea wrt the BazaarOfViolence : http://globalguerrillas.typepad.com/globalguerrillas/2004/07/stigmergic_syst.html
Should TagCloud-s (FolkSonomy) be thought of this way? - see BillSeitz:PeterSmall
In BiologyAndComputing, SteveBurbeck points out that multi-cell organisms are based on StigmergyStructures. Essentially, the cells are temporary; bodies aren't just a bundle of living cells, they're a bundle of ephemeral living cells which are connected and communicate stigmergically through the non-living persistent structures (eg. bone) "we're termite mounds" (or corals?) ( (WarpLink) PersonalIdentity )
Burbeck is explicit that things like tagging are examples of stigmergic information transfer. As is wiki. And JonUdell suggests PageRank allows the whole web.
But then, what communication isn't stigmergic? Writing must be - ie. we leave writing around the environment. It seems like speech shouldn't be. Is there a MediaAndMaterials question lurking here? Eg. that some sorts of communication are "more stigmergic than others" and this can bias the overall system behaviour in certain ways? (Hey, I claim BonusFreakyConnectionPoints for this ... although that was actually prefigured by a link to WatchingAnts already on MediaAndMaterials, amazing!)
Spiders outsource cognition to their webs.
See also :
Added 2020-05-15 : Originally 2017-11-22