Okay, after molesting Siri's files a little, I found a little entertaining something. Go to Springboard.app and locate any random language folder, e.g. English.iproj. Edit the Assistant Strings file at the line "Assistant_Not_Available_Title" and "Assistant_Not_Available_Subtitle". You will get something like the pictures below. Wonder if someone can help me make a tweak that allows you to change Siri's strings? Okay, the website is not valid, but it is meant to be 1) a joke and 2) a wild goose chase for less intelligent beings.