An excerpt from Wikipedia:
* The un-restrictive terms of Android's license have allowed corporations using Android to place restrictions on their own customers. As an example, tethering (PC or laptop internet connectivity via the cell phone) is forbidden by T-Mobile USA, and the Android Market has de-listed such applications for T-Mobile customers. This also means that the apps can be carrier-specific as chosen by Google.. (As a note, users can still download any application that is hosted on the internet whether or not it is in the market).
* Android uses Linux as its kernel, but according to Google, it is not a conventional Linux distribution. It does not have a native X Window System, nor does it support the full set of standard GNU libraries like its system libraries (GNU C Library). This specific modification makes it difficult to reuse existing Linux applications or libraries on Android.
* Android does not use established Java standards, i.e. Java SE and ME. This prevents compatibility among Java applications written for those platforms and those for the Android platform. Android only reuses the Java language syntax, but does not provide the full-class libraries and APIs bundled with Java SE or ME.
* Because of potential security issues Android does not officially allow apps to be installed on, nor run from, an SD card. Current Android products such as the HTC Dream and Magic have limited onboard memory and many users feel restricted by this lack of functionality. Several unsupported modifications exist, however, to give the user this capability.
* Android is criticized for its multitasking abilities and the lack of a significant driver base. For these reasons ARM and Real have expressed doubt that it will gain a major market share as a netbook OS.
* Responsiveness can be poor due to the limitations of Dalvik's automatic memory management.
* Developers report that it's difficult to maintain applications working on different versions of Android, because of various compatibility issues between versions 1.5 and 1.6.
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