Good question, and I know of companies that have done both, but my opinion is to understand the entire problem first, then submit a change request.
I believe it is important understand and document all the impacts onto the form, though I have seen complex forms and simple e-mails used.
I have believed I you should be able to speak to an issue intelligently prior to starting some kind of fire in the process. It has always seemed odd to me to start a fire in a process then not be able to explain it; it gets folks all worked up for no reason.
Other PMs may have another opinion.