I have seen a problem with the way the Android system handles iframes on my particular tablet, the Motorola Xoom. In the most recent versions of Android, the system browser does not pass click events to iframes that overlay plugin media. You can reproduce this by creating a Web page that has a Flash movie covering the entire page and an iframe in a layer above the Flash movie. Touch events, including taps, will not be sent to the iframe at all.
Someone was kind enough to test different versions of the system on the Xoom for me. This behavior was not in the Xoom with Android 3.0.1. It showed up in the Motorola Xoom running Android 3.1 or higher. The version of the Flash player had no effect.