In a strange turn of events this week, some Model S owners have reported that their new cars have shipped with new lane departure and speed assist sensors. See TeslaMotors.com forum post and teslamotorsclub.com forum post for more details.
Update: Tesla has issued the following statement, "Starting recently, some Model S being delivered in North America come equipped with two new features. The features are lane drift detection, which will deliver a warning via vibration in the steering wheel if the driver starts to drift from the lane without signaling, and speed limit display, which will inform the driver of the speed limit and alert them when it is exceeded. These features are necessary to meet the latest standards in the European market, but we have decided to integrate them into Model S delivered worldwide." Also, regarding retrofit possibilities, "due to the extensive changes involved in this instance, however, a retrofit is not feasible."
Iowa's Department of Transportation told Tesla to cut short a test drive campaign they were doing in West Des Moines. Supposedly Iowa law prohibits carmakers from selling directly to consumers. Tesla's reply: "A spokesman for Tesla said the company does not believe the statutes apply because the company was not selling cars, only providing test drives."