Any code changes take a non-trivial amount of time. It sounds like the solution is to delete more of the cookies on logout, but there may be other Facebook services that use them and need to be transitioned away.
>Any code changes take a non-trivial amount of time
Thats a awfully cautions attitude and smells like a huge cop out for the well known fly-by-the-seat-of-your-pants commit to live strategy that facebook has.
I don't work there, but where I work we deploy 10-20 times a day and if somebody asked me to change the way we store data in cookies, it would probably take a bit of time to roll out.
I'm only defending them because it annoys me when people who aren't familiar with the software internals tell me "this is a minor change, it should take you less than an hour".
To be fair though, not doing something is a lot easier to implement than to add new functionality. As a minimal implementation they could err on the safe side and stop tracking everybody for a bit until they've corrected their error.
Whatever you've read, Facebook likely has a non-trivial push strategy, just like everyone else. Nobody at their HQ is committing directly to the live site.
Facebook's Release Engineering blog says a code change can go from commit to live in less than 60 minutes. Admittedly, they don't say how often they deploy.
