Yesterday I gave a talk at ETech 2008 entitled "Mobile Social Software from the inside out", which was an updated version of my overview of the issues (and some solutions) regarding multi-user location-based applications. People interested in the slides can have a look at the annotated version I've put here (pdf, 14.5Mb). The reason why I gave an existing talk was that I've never presented that one in the US (only in European countries and South Korea) and was curious of the reactions.