Random stuff banned for random reasons (main ones being "use our silly verbose and limited library instead", "templates are bad because generic programming is too complex for people outside of the A-team", "I get to set the guidelines and I don't personally like it philosophically, so I won't allow anyone to use it").

For example, no exceptions. Exceptions are a core part of the language and are fundamental to many of the features and or in maintaining invariants.

Not having exceptions means that all Google components are inherently useless in normal C++ unless they wrap them up.

The style is designed to dumb it down to make it usable by everyone who never had C++ training. For that it's valuable, but shouldn't you want your developers to be proficient with the tools they use anyway?