Just curious. How does one "verify" that a guest brought into the lounge stays in the same room as the member?
In the US, where occupancy and formal guest registration are not usually controlled, I wouldn't expect any issue bringing in a guest who wasn't staying in the same room. In many other countries, per comments by others already, it may not be possible.
Of course, given the quality of Marriott lounges in the US, this is less of an advantage than it may sound.