This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
While I acknowledge that security is not the first subject one would focus on in a beginner's book, I take issue with the way this is phrased. Mobile development generally means a) a distributed system (the device accessing one or more servers), and b) the device can easily get lost or stolen. Both these are cases where one needs to pay particular attention to security. So, when "writing Android apps", one should never lose sight of these issues. (Stepping down from my soapbox now :-)
I agree with those concerns. For example, for point-to-point communication, an app developer would just use SSL, like on any other platform. For lost/stolen device, Android provides Device Management capabilities which are part of the operating system.
So, from those two points of view, platform takes care of this (just like any other operating system) and an app developer does not need to worry about those particulars.