Should corporate communications officers act as spokespeople in the media?

This question came up in conversation with one of my clients recently. Where do you stand?

Pros:

1. Comprehensive messages – The corporate communications specialist (=VP, Director, Manager, etc) is likely to have crafted the messages (or been in charge of it). They will have a good grip on them.
2. Frequently available – The Senior Leadership Team (SLT) is frequently traveling or busy running the business. Clearly there are circumstances when the SLT needs to step up, such as during a crisis. But for less urgent media appearances the corporate communications specialist is more likely to have time.
3. Excellent communicator – You would expect the corporate communications specialist to be the highest skilled to communicate the message (in theory).

Cons:

1. Senior decision maker – As a TV producer at CNBC, corporate communications specialists were the last people we would accept on the show, and then only if no one else from the company was available. We really wanted a key decision maker to appear.
2. Substance – Our fear was always that a corporate communications spokesperson was just going to give us a sales pitch or the corporate line.
3. Known personality – The CEO is likely to be well known, unlike the corporate communications spokesperson. You can probably imagine advertising on your channel: "We have the CEO of Amazon on the show tomorrow!", but not "We have the VP of Corporate Communications of Amazon on the show tomorrow!"

What do you think?