Library service evolves with the advent of new technology. Possibilities of harnessing web based services are immense. Library 2.0 is a concept borrowed from Web 2.0. In other words, Library 2.0 technologies are mostly web 2.0 technologies. Kano had established that introduction of unexpected services leads to excitement. however, in due course of time the exciting service becomes routine. These paper attempts to describe library 2.0 technologies as Kano's exciting factor which will eventually become basic expectation without which users will be disappointed with the library services.