According to blogs, this has been available since 2005 or 2006. According to the company (which is not google, but a private flight information source), this information was updated in mid-2006. So this isn't new. Again. Therefore, while worrying about this is probably a good idea (to some extent at least, make sure the information is delayed well enough so it's useless or something like that), this isn't a new problem but at least a two year old one.
Malaysia sends team to Reunion Island to see if aircraft debris is from MH370 flight (Reuters)
from the article: Web service that tracks flights could assist terrorists