[notaddicted]

http://lmgtfy.com/?q=manufactured+homes&l=1

less snarky answer: mobile/prefab homes are more common where the land is cheap, and places where a lot of people live, the land isn't cheap. I've never seen one where you can't tell (or have I?!? but seriously, probably not,) but I've been living in the city for years.

[WalterBright]

I know that prefab homes have a reputation for poor quality.

But I see no fundamental reason why this must be true. Automation in every other industry increases quality, and certainly predictability. In current home construction, quality varies erratically all over the place, even in the same home, even in expensive homes.

[ajross]

This is exactly it. The cost of new construction in urban environments is dominated by capital, not labor. So there's no reason not to design a custom house or building vs. buying a prefabricated one. And that drives down the volume of manufactured housing, which drives up its cost and hurts competitiveness further.