What is the need for registering multiple domains?
It is a strategy for businesses to protect their online identity is to register multiple domain names. Basically, when you have a great idea, why let somebody else have a free ride on your tail? You're still only spending about Rs 199-1500 a year to eliminate the competition!
For example, if your business name is bookshop.com, a business could register a variety of domain names - such as booksshop.com, books.com, bookshop.biz - and the list goes on. Consider the singular and plural forms of the domain name, and the hyphenated version(s) if these are obviously interesting. There's no need to go crazy on alternative extensions, but make sure you buy the .com, .net and .org versions of the domain, plus alternates if available. These multiple domains can easily be "pointed" to your primary domain name.