I just tried linking my Marriott Rewards account to my Twitter and Instagram accounts, and 100 points (25 x 2 for linking to Twitter/Instagram + 25 x 2 for following MR on Twitter/Instagram) instantly appeared in my MR account.
I also did 5 tweets with #StayBaltimore and #MRpoints, and 125 points (25 x 5) immediately appeared in my MR account.