When someone tries to compare OSM.org and any cartographic web service (usually, Google) it is hard to make people trust you when you telling them it’s nothing more than technical website mainly intended for internal use by mappers. Same problem applies to OSM Standard (aka Mapnik) style. Finally, there is something more or less official to show them as a proof.

Andy Allan just gave this reply on question about expanding tile distribution infrastructure. (Full message text with added emphasis.)

We should be clear here - we have more than enough capacity to handle all the traffic generated by our mappers, editing software and every website run by the OSMF, local chapters and local mapping groups. Several times over.

We’ve always allowed other people to use our spare capacity on the tileservers, but recently it’s got completely out of hand. Most of the use of our tileservers has become developers looking for free maps, nothing to do with the rest of the project. Often these are commercial companies who are using our tileservers and selling their apps. Subsidising commercial companies isn’t the best use of community donations and volunteer sysadmin time, when there are many alternative services (such as those run by CartoDB, Stamen, etc) that provide zero-cost map layers based on OSM data anyway.

We do have plans to scale the tile infrastructure later in the year (cascading an old database server), in addition to the current process making sure that our OSMF tileservers are being mainly used for OpenStreetMap related projects.

I just want to keep it here to be able to quote it for any stubborn people, insisting on their own view of OSM infrastructure functions.