The load() command in the mongo shell does not currently support expansion of ~ paths to the current user's home directory:

> load("~/foo.js")
2014-11-11T14:38:41.124+1100 file [~/foo.js] doesn't exist
2014-11-11T14:38:41.125+1100 Error: error loading js file: ~/foo.js

From the error message it's not entirely obvious why ~ doesn't work. The expectation is that ~ would expand to the equivalent of $HOME similar to shells like bash/zsh (i.e. "/home/user/foo.js").

Tilde paths would be useful for writing mongorc.js add-ins that can load from the user's current path. For scripting purposes, it may also be helpful to expose a getter for the $HOME directory path (eg. getHomePath()).