When we talk about Sugestion Box in Japan, it reminds us Shougun Yoshimune Tokugawa who is reported to introduce Meyasu-bako (Suggestion Box) first in Japan (1721) collecting various suggestion such as setting up a hospital for poor people .
So it is very traditional and common way to improve the organization effeciency in Japan. Toyota is one of the companies which has introduced Suggestion box. In 1980s they collected 800,000 suggestions yearly - 17 per employee and equivalent to US$230mil annual cost saving.
The key sucess factor of this is to advocate employees to paticipate in the management.
So in order the employees to have the ownership of the company and contribute it's efficiency actually, Suggestion box becomes one of the effective tool.
Suggestion Box article http://www.breitnerandassociates.com/PDF/Think.pdf