Well, one downside that I see is that people get carried away with categorizing other people's modern profiles. A profile in the 20th century which happens to be open is not really benefited by a far-distant stranger coming along and dropping a name study or location category in it.
The person who manages that profile is well aware of the location and family name that the category indicates. I am sure they do know that there are millions of unrelated people who have live in that particular county at one time or another.
They are probably the only person who has an interest in that person whose profile just got pointlessly categorized. It is extremely unlikely that even the stranger who categorized it will ever come back and add any research value to that modern profile.
So I think it would be best to use discretion about sticking to the ancient profiles, when categorizing other peoples work.
Also, when I am looking at a location category, why in the world would I need to see the names of thousands of 20th century people cluttering it up? I would instead want to be looking for names of ancient profiles, to find the roots of modern people whose ancestors may have come from that location, where the roots are uncertain, for example.
But if Joe Smith lived there as recently 80 years ago, because his parents happened to move across the country from some other remote region, the category fails to be useful to anybody on that modern profile, and is more genealogically misleading than helpful.
