I don't think this is just an IT issue - too many times have I seen someone ask a manager about a process or requirements for something when the manager is so far away from the day to day work that the answer they give is misguiding or just plain inaccurate. Managers need to be asked because otherwise they pout, however, you cannot beat the answer given by an experienced and competent user within a department for determining what is actually required.
So it's not just
CIO: my guys need hadoop because our volumes are huge
DBA: our data is tiny but we're having some real load time issues due to network throughput
CFO: my guys needs a wizzy visualisation tool to help them build financial reports
Accountant: I wish I could secure some of our trainer's time so the juniors could use excel better
Sales vp: we need a system that allows the sales teams to access their work computers on the road
Sales guy: the folks we're selling to want to see some sample reports - can you build me some so I can produce some print offs the day before?