Maybe things get clearer if we get rid of the idea of “a default renderer”. We should look at name= as a kind of fallback-value which will be used if the language the map-user wants to read is not available.* The fallback values for streets in thailand surely should be the thai names of the streets. But the fallback for a supermarket like 7eleven should be the value 7eleven. Please take into account that not only thai people look at OSM-maps of Thailand. Chinese people will do, Germans do, the whole world does it.

EDIT 15.05.2010 (I try to describe it better and easy to understand.)
The name=* is very important as fallback value for users all over the world, as long as not all languages of the world are available. So we should try to put a useful value for users of the whole world in name=*.

(This rule should not be applied to streets and places of course. For streets and places the thai name should go into name=*)