[kenbellows]

I'd like to define it pretty broadly, but it could certainly be narrowed down if there's a consensus among users that it's too broadly defined, like you're saying. In general I would define a cheat sheet as a quick reference guide with easy access to useful bullet points that are pretty universally applicable, i.e. things that everyone should know.

[jpasden]

I'd consider portability. My favorite cheat sheets are images or PDFs (one page only). Adding an element of graphic design can really upgrade a cheat sheet.

(Do some searches for cheat sheets in Google Images, and you'll see what I mean.)