"One of the most basic conundrums in computer security is the constant trade-off between security and usability.  At the end of the day, if security is too complicated to use, then it simply won't be used.  Even if a feature offers a good level of security protections, if it is complicated or has poor usability it will likely be disabled by the end-user or network administrator, which doesn't benefit anyone..." - Jim Allchin

http://windowsvistablog.com/blogs/windowsvista/archive/2007/01/23/security-features-vs-convenience.aspx

Very good and informative blog post!

Urs