Marriott no longer sends these by mail. They apparently don't even send an e-mail notification. However, what you should find - in your Marriott Rewards account - is a "Requested Reward" for the e-certificate.
Mine showed up in my account on March 3, 2008, within a few days of my second anniversary date. To find it, log in to your Marriott Rewards account and click on "Marriott Rewards Activity". For the "Select a month" drop-down box, select (at the bottom) "Last 6 months", or some similar lengthy period and "Show" "All transactions".
What you are looking for is something that looks like the following:
03/03/08 PREMIER VISA ANNIV 1-5 HOTELS 0 pts
The electronic certificate is known to Marriott reps as a "43J" certificate. I just made a hotel reservation using mine this morning. You'll have to call to make the reservation. You can't do it online.
Be forewarned, that until Marriott fixes the problem, your online reservation made with this certificate will likely show that "You do not have e-certificate(s) for this reservation. blah, blah, blah" and that a Standard Hotel Reward for xx,000 points is applicable. Nowhere does the reservation state that it's a free night or that a free-night certificate (instead of a xx,000 points certificate) will be used.
Because I like to have proof of such free-night reservations in hand, I talked to 4 reservationists, one supervisor, a Marriott Rewards supervisor and one Customer Care supervisor this morning, trying to get the reservation fixed - at least what I could see online. All to no avail, except for verbal assurances that the reservation included the 43J certificate and that I wouldn't be charged any points, along with a suggestion that, if there is any problem at check-in, I should refer the desk clerk to the notes section of the reservation.
The bottom line is that there is a glitch in Marriott's system. Thus, ensure that the reservationist adds to the "notes" section of your reservation that an electronic 43J certificate - not points- is associated with the reservation.