Not using C++ exceptions in Google's code bases is partly due to historic reasons (since the original code base did not have it), and partly due to them being "harder" to implement in C++ correctly.

They even acknowledge in their C++ style guide[1] that: " Things would probably be different if we had to do it all over again from scratch."

[1] http://google-styleguide.googlecode.com/svn/trunk/cppguide.x...