I may have missed it being discussed here (and if so, I apologize), but I was just able to secure both the regular Amazon store app on my Kindle Fire as well as the Amazon Android Marketplace to prevent my kiddos from buying things when they are playing with it. (Has the Android marketplace always had parental controls or is it a new thing?)
For the store portion, I followed these instructions:
http://fireapps.blogspot.com/2011/12...hases-and.html
Then, I went into the App Store while on my KF and hit the menu button, then Settings, and set up the Parental Controls and disabled in-app purchasing.
The good news is that the app store settings were universal and I was able to do it on my phone as well. Which I assume means I'll also be able to do it on the Coby Android tablets I got my boys for Christmas.
Looks like one of the big complaints has been resolved as far as I can tell.