Let's take a step back for a second. Remember your first day on the job? Part of your orientation with HR probably included being given an employee handbook of sorts. The handbook spelled out all the behavior expected of you during your tenure with the company. Aside from giving you the bad news that jeans are not considered business casual attire, it also likely included a section regarding IT policies. Many companies expect employees to refrain from using company property (i.e., their PCs) for personal use, such as email and Web surfing. There is probably also language about making sure that sensitive company information is never exposed to outsiders.
Typically you have to sign a document stating you have read the handbook and will adhere to the policies contained therein. But who actually reads the darned thing? If you haven't read the handbook, you may not know that there are security policies that have to be followed with certain corporate data. That doesn't excuse employees from not taking appropriate action, though. Common sense needs to come into play at some point.
On the flip side, there is a lot IT can do to secure enterprise systems. Any good IT center will have this well in hand. There are innumerable solutions IT can use to protect both the hardware and data from being breached. For instance, Mobile Guardian, from Credant, is one such solution that provides end-to-end security and lets IT enforce policies like passwords. IT does need to educate employees, though, on what is acceptable and what is not. Simply installing software on employee laptops and letting them butt their heads against policy controls won't work.
In the end, it has to be a partnership between IT and the employee. Are many security policies annoying? You betcha. But they are in place for a reason.