I believe it is also unlucky to give someone a clock as a present in china as teh word for clock is similar to the word for funeral. I guess if you gave someone a clock set at 4 minutes past 4 , you woudl be sending a pretty strong message!! I don't think its any more "stupid" than 7 being a lucky number or 13 being unlucky. It's just cultural. I remember as a child spilling salt,dropping a knife, walking under a ladder etc all had connotations attached!

Also, floor 4, 14 etc do exist in Hong Kong and often attract cheaper rents!!
I also believe a building next to a hospital or graveyard is also unpopular.