We have extended json syntax for most types, see http://docs.mongodb.org/manual/reference/mongodb-extended-json/
There are two flavors: "strict" and "shell" mode.
Yet when certain types are printed in the log file, they don't comply to either of these formats, instead using arbitrary syntax that is hard to parse and cannot be simply copy&pasted back into the shell.
All types should be printed as strict or shell syntax in the log for consistency. Preferably shell syntax since mongo shell can't yet understand strict syntax (see related ticket, SERVER-6813).
log file (would be misinterpreted as floating point value)
log file (quotes missing)
And so on.