> use OpenStreetMap because clearly Google maps doesn't work for them (cost presumably).

I worked on the map feature while at Craigslist about 6 years ago. Launching this on their own servers at the time (vs using Gmaps, which was the obvious choice) was a serious and important technical feat.

The decision to use OSM (as far as I remember) had to do with supporting open source (The company made a donation to OSM right after launching), keep user data within its servers and (as a distant third reason), keep the style more homogeneous with their layout.

Funnier still because Craigslist themselves have filed multiple lawsuits against such mapping sites (e.g. PadMapper) for scraping their site for listings.