I disagree, In a short while the hackers will find the exploits and grandma will be forced to update her Android phone just to protect her "depends" behind. That the Android will come to be a behive of Virii and worms and other nasties is because it is so open. The code is out there, open to the world to study, and there is no app gatekeeper testing what may be downloaded to the phone.
These are the same arguments against *Nix that people used to throw around. Yet, *Nix remains one of the most secure operating system(s).
Basically, your spouting FUD.