The YAML parser in the server can consume JSON syntax in the expected fashion, and although this is technically covered by the YAML specification it is an unexpected feature for many people. We have had several customers ask about this and some incorrect information has been supplied because the JSON support was unknown at the time.

It would be nice to advertise this powerful feature a little more, so I propose a note to this effect on this page:
http://docs.mongodb.org/manual/reference/configuration-options/#config-file-format

I would like to explicitly call out that the file can be written in JSON syntax and it will mean the same thing. For example, the following is exactly equivalent to the example configuration given on that page:

{
 systemLog: {
  destination: "file",
  path: "/var/log/mongodb/mongodb.log",
  logAppend: true,
 },
 storage: { journal: { enabled: true } },
 processManagement: { fork: true },
 net: {
  bindIp: "127.0.0.1",
  port: 27017,
 }
}