Seth Godin had a post about lazy slogans and headlines that feels pretty applicable to organizational mission statements, branding, and many marketing terms used by arts and cultural organizations.
If you can swap your slogan with a competitor’s without changing the meaning of either brand, then your slogan is meaningless.
For example, “You belong here” is not a positioning statement for a college seeking new students. It’s just noise.
It also doesn’t help to mix weasel words with more weasel words and then add specifics. On charity’s pitch: “Your contribution can help up to 35 people.”
“Up to” covers a lot of ground, doesn’t it?
The bit about swapping slogans with a competitor and there being now meaningful change to the brand seems particularly applicable to mission statements. If they are so easily interchangeable between two organizations, then is there is a compelling reason for both to exist in the community?
The fact that a lot of organizations may not pay close attention to their missions may be the only saving grace in that what they do in practice may distinguish them quite a bit from the competing organization. If that is the case, there probably needs to be some introspection about aligning the guiding principles with practice.

