Const references in std::vector elements

The vector elements must be assignable. From section 23.2.4 Class template vector of the C++ standard:

...the stored object shall meet the requirements of Assignable.

You may want to check

std::reference_wrapper

available with C++11

No, because you can't assign to a const reference and the STL containers make use of assignment for moving items around.

You're better using a shared_ptr (boost:: or std:: depending on your environment) or a raw pointer.