Perfect forwarding fails when template type deduction fails or when it deduces the wrong type.

There are several scenarios in which C++11’s move semantics do us no good:

Reference collapsing occurs in four contexts: template instantiation, auto type generation, creation and use of typedefs and alias declarations, and decltype.

Universal reference parameters often have efficiency advantages, but they typically have usability disadvantages.

Overloading on universal references almost always leads to the universal reference overload being called more frequently than expected.