If you want this functionality, you can get it by sending moot $20(U.S.). You are then given the URL of a secret activation page and a unique code to enter there, which will store a cookie in your browser, allowing you to access fortunes any time you visit /b/. The downside is that if you want to use it from more than one machine, you must pay again to get a new code, since each code can only be re-used from same IP address that used it the first time (this also means that people on dynamic IP are screwed if they delete their cookies).
If you're interested, e-mail moot or else ask in IRC (probably better, since moot gets a shitload of e-mail).