I do not believe that IT should be deciding what is or is not permissable. And I think, to a large degree, we're all in agreement.
If you don't think that IT has a role in determining what is or is not permissable then we are not in agreement. The policies at a company are usually set by upper management with input from numerous departments. Legal gets to weigh in on issues where liability could come up. HR gets to weigh in on matters where their expertise is relevant. IT also should weigh in on areas involving technology. Because IT has become so prevalent these days, I think you'll find that our interests cross the boundries from simple security into legal and HR protection as well. Also, because we are experts in the IT field we will undoubtedly have legitimate concerns that should be addressed through policy, and because other people who help set policy are not technical experts these concerns usually are not addressed until/unless IT brings them up.
Now there is a particular subset of people who are of the mindset that IT is customer service, that their purpose is to support the company, and that they could be treated like facilities or a utility service. In other words, they feel like they should tell IT what they want and IT should implement it. But when you think about it the problem with this mindset quickly becomes obvious. While everyone may know what sort of office/cuble layout works for them, or where they need power outlets, or how many bathroom stalls there should be, the average employee or manager really has very little grasp of the subtleties of IT. If we were to let various managers and departments choose their own path then IT support would be a nightmare with different hardware, software and training standards.
That's why IT has to bring their expertise to bear and steer the technological ship. Department managers don't dictate to HR what benefits their employees should get, neither should they dictate to IT what services the company should provide and support.
Now we're not the only people who are talking about this. In the past 5-7 years there has been a big push in the industry to get CIOs a seat at the big table. Even though they have a C-level title, for the longest time they were considered below the CEO, CFO, etc. But what companies are beginning to discover is that IT isn't a simple utility like facilities or water, but a key asset and a potential competitive advantage. If a company allows IT to take a leadership role in areas where they have expertise, they can work with the rest of the company to define a long-term technology plan that becomes a competitive advantage. These companies tend to meet with much more success that companies who look at IT as subservient to other departments. Companies that do not embrace IT and the capabilities that they can provide typically find themselves unable to compete with companies that do. And when I say embrace IT, I don't mean "make sure everyone has a computer with network access on their desk." It's the difference between looking at IT as a partner or as a servant.
I'm firmly in the "IT as a partner" camp, because I have worked for and with companies on both sides of the coin. I've seen companies that embrace and partner with IT flourish, and I've seen companies that were run into the ground because they didn't.