Free rider problems/tragedy of the anticommons - research that isn't directly patent-able would result in a dearth of private investment because there isn't a comparative advantage in researching it

Tragedy of the Commons - Research into monitoring, maintaining, regulating, and improving resources shared by private companies

Positive externalities - Some research will not pencil out without including return on investment that cannot be captured by a company

Negative externalities - Companies won't invest in research to reduce injury to other parties (could fix with regulation also but depending on specifics this may be very difficult to enforce)