I agree, having lived in that region. There are no problems with 5; that poster was mistaken. The number 4 is unlucky in much of East Asia because the Chinese character for 4 sounds the same as the one for death. 7 is a very lucky number in much of the world and, in other places, so is 8. But I think the crazy eights 88888888... looks idiotic. If you're going to use 8, then make it a nice round 800,000 or 8,000,000, etc.