In short: FB employees get to see the new features first, and are encouraged to submit bug reports.
I imagine there would be some utility in knowing whether FB employees use your site/app. Though there'd be some complex cross-domain issues to solve first.
Honestly I'm not sure. Facebook's crossdomain policy disallows access from external domains, so you can't load this from a random Flash or JS script.
Hm, I think you can still invoke it jsonp style and overload the Object constructor in older browsers though, right? This would not only tell you whether they were a FB employee, but perhaps more importantly, their facebook UID without needing them to agree to any OAuth access.
That only works if it's surrounded by parenthesies. A bare object literal is not syntactically valid JavaScript.
i think jquery can deal with a straight json response, but i may be wrong.
I assume there's a flash app in the company intranet which checks if you're still hired every hour.