Normally one. That means a company with one website/domain can offer all its services/goods. One option can be in order to protect its name all Tlds with that name can be registered. i.e for banks, airlines .. etc.
Depends on your business as well if your business is all over the world so better have website and domain for all countries you do business on else one site and domain can work for you. Business all over the world doesnt mean that if you sell domain names and you develope website for each country but some physicall business like if you have chain of restaurants in many coutries so better have there websites diffrent and domains as well.