My experience is inline with the first response. I believe I made the reservation via the website, and then called the hotel to provide the update on who/etc. There may have been a fax/email involved as verification of this (it has been over a year!)
I've also frequently done this. Customer Service can assist you with making the reservation in the other person's name, then transfer you to Rewards line to issue the eCertificate for the stay. They then just need to show up with ID and a credit card to cover the incidentals as mentioned.