This 99.99% thing is a dangerous fallacy, dangerous against freedom. See the law: you have the possibility to sue the government, in free countries. Only one person in hundred of thousands will ever need to sue for real, but having this open door is what defines freedom.

By the way 99.99% of all android users is quite a crowd, it could fill a few cities, so if they do check the code it can and will influence other android user, if only by adding pressure on Google. You see, adding a backdoor to android is really much harder for Google than it would have been with closed source, maybe 99 times harder?