An interesting (contrarian) take on the whole "get a business analyst to document requirements and have the users signoff" process
Basically, the author says it's completely the wrong way of doing it, and IT should be more customer-focused instead.
This is an excerpt:
"IT leadership usually hear the customers complaints and react by trying to 'nail down' the requirements even harder by more rigorous and complicated methodologies changes. More meetings, more documents and especially 'signoff' contracts to force the user to agree on what will be done are an attempt to deflect any finger-pointing later on ... putting more emphasis on the 'what I need' point is view is more difficult but ultimately the right thing to focus on."
I experience this sometimes when a company first installs a new technology like SharePoint their own without any expert help, signs off on the requirements only to express that they really want something different. This is why it’s important to start off small in an organization for them to understand the technology and more importantly this is why a large company without SharePoint experience should bring in external assistance when deploying SharePoint, so the right questions get asked at the right time.
But that idea is so anathema, it's unlikely to happen anytime soon, especially in large organizations, obsessed by documentation and red tape.