Upgrades help improve a site’s performance, stability, and security. Having a WordPress ugraded whenever it has one is very beneficial since old WordPress version may be the target for hackers. ICANN or Internet Corporation for Assigned name and Numbers was recently hacked because they failed to upgrade their WordPress. ICANN is a high profile blog, they may have solved the problem already but what if it happens to your site?
WordPress releases patches and fixes whenever they released an upgrade. While users have a choice whether to upgrade or not, it is recommended to perform an upgrade immediately or be hacked like all other bloggers that fail to upgrade WordPress.
Read full story here: http://wphacks.com/the-importance-of-upgrading-your-wordpress-installation/