  We discuss the criteria presently used for evaluating the efficiency of
quantum teleportation schemes for continuous variables. Using an argument based
upon the difference between 1-to-2 quantum cloning (quantum duplication) and
1-to-infinity cloning (classical measurement), we show that a fidelity value
larger than 2/3 is required for successful quantum teleportation of coherent
states. This value has not been reached experimentally so far.
