I found this article on how Google manages its internal IT fascinating. Google basically sets its users free to download software from the Internet, among other things, and take care of themselves. Imagine that.
Of course, Google can do this because Google is, well, Google. Google is heavy on engineers who understand security. This is becoming less and less true over time, however, which brings to mind the real reason Google can have a policy like this:
It trusts the system, not the nodes within the system.
Done right, this sort of policy reflects the obvious--there's not much IT can truly do to protect users from themselves--and sets employees free to experiment, which is critical to a company like Google's success.
Maybe for a financial services company it's less important that it experiment in this way. But for a technology company...critical.