advantage of web 2.0

• They support collaboration across time and space.
• They are easily accessible and easy to use.
• Many people already have a comfort level using them.
• They are low-cost (sometimes even free).
• They do not require much IT support. 

reference 

http://content.arma.org/imm/JanFeb09/Walk_In_The_Cloud/web_2_benefits_considerations.aspx