There are different kinds of imports. Safest are those done by hand, but also the dirtiest, in my opinion: it's easy to miss or to get lazy and just press upload.
For towns and villages, the best source we had was GNS, an american database of toponyms. I converted it to OSM format and wrote a short manual on copying it onto the map:
Interesting that while box=yes parameter doesn't work on osm.org nowadays, parameters minlat, maxlat etc still do.
@zverik Still loads of redundant GNS tags on place nodes in Ireland (probably imported by Dermot - mackerski). Until the townlands project got going they were still the major source of places in rural Ireland. Still a lot of dedup & other cleanup needed.
I also did a bit with them for Pakistan, but never could trust the data in a country where the population had increased so much : http://sk53-osm.blogspot.com/2011/03/garmin-overlays-of-gnis-names.html (probably should correct GNIS->GNS