var options = { path: myPath, domain: myDomain }
// Then somewhere in the code:
$.cookie(key, value, options)
// And then somewhere in another place:
$.removeCookie(key, options)
// At this moment our options are extended with {expires:-1}, so:
$.cookie(key, value, options) 
$.cookie(key) // undefined: it expired right when we wrote it!

// Bad:
$.cookie(key, '', $.extend(options, { expires: -1 }));
// Good:
$.cookie(key, '', $.extend({}, options, { expires: -1 }));