The biggest issues are that you probably won't earn any credits for nights or stays and that you might not get your elite
status perks honored.
You won't earn Marriott points when you book through online travel agencies (OTAs) but you can still get your elite
status perks honored.
Not exact matches
A few exceptions do apply such as Hyatt's Guest of
Honor program but opportunities are usually limited to share the
perks of your
status.