Does your Mission stand as that beacon for those already involved with the organization -- a litmus test for performance? Or does it stand out there to tell prospective customers what you're all about?
It is a fine line between the two but a line nonetheless. Certainly the intent of your Mission is the same regardless of what audience you craft it toward. The difference, though, is in the voice, tenor, and attitude of the Mission. Those things make a big difference in how someone receives and processes a Mission Statement when they read it. In the case of "insiders," that can make a difference as to whether they are spurred to supportive action or lulled into complacency. For "outsiders," that nuance can make the difference whether they check you out or not and, if they do, what attitude they come with.
I was speaking to a good friend of mine recently for whom I have great respect. He owns a business with his brothers. They have a Mission statement but he is pretty blunt in telling everyone not to expect a lot of strategic verbiage from themselves beyond that. This is because they set the overriding goal out there, hire good people, and let them explore and figure out how to be successful.
I like that.
But the question still remains as far as with what "voice" a Mission Statement is written. Any ideas? This topic is worthy of a lot of fleshing out, I think.