Marriott Rewards has been sending out emails today prompting members to add their phone number and email address on file.
Apparently, you will need an emailed code in the future when you try to redeem for certain awards (I would assume those to be merchandise ones that make very little sense for anybody else than for fraudsters).
You can access Marriott Rewards here.
Hotel and airline loyalty program account take overs have been a hot topic for the past couple of years. Club Carlson and Hilton HHonors had huge issues having third parties taking over accounts and draining the points for merchandise (at terrible value of course).
The phone number that I have on file with most of these programs is pretty useless because I am traveling 100% of the time. I have Google Voice set up that should theoretically ring at my cell phone wherever I am as long as the data is turned on.