Ah I understand now.  Was a bit confused especially with this small block of houses which probably should also be marked landuse=residential as well.  Anyway at least what I'd do is match to neighborhood delineations (usually fencing or roads) but probably would leave alone anything that's at least technically correct.  I'd probably only make one big blob of residential only if it's a new block of houses and I don't know if they're related by development name or not.