I have frequently used corporate rates on personal travel, especially in high cost locations, for Hiltons, Westins, Intercontinentals, etc. Never really gave it much thought until now.
Also must state that not once can I recall being asked for any form of identification, or even being questioned about the rate. Not that it would be too much trouble as the rates are always those which I would be entitled to use on company travel (never asked about personal travel).
Something to ponder, although it probabaly won't change my habits.