This question was asked by a commenter last week.

And the answer is 'no'.

Because the danger is that whatever the CD writes, they will think is brilliant. This is normal - we all think our own stuff is brilliant. But normally, there's a CD there to tell you it's actually piss-poor... unless you are the CD, in which case everyone will tell you it's great, because you're their boss.

The agency will have lost one of the most important advantages of the CD system: objectivity. And it will most likely have gained a bad ad.

The boss actually thought his own ad was pretty darn good

Furthermore, if the CD writes something, and it gets bought, who's going to make it? The CD won't have time, so it will probably get shoved onto some young team. Which will be awful for them. No one gets into advertising to make someone else's ideas, everyone gets into advertising to make their own ideas. And they won't do as good a job as if it were their own idea - we all do a better job when we feel ownership. 

I understand why CD's sometimes write ads. Sometimes, they just want to. (Ego.) Other times, they're frustrated because they feel their teams aren't producing the goods (which in reality is their own fault). And sometimes, they want to 'set an example' to the teams. (Ego again).

But probably the biggest reason is they want credit. A lot of the work a CD does - working with the strategists to refine a brief, working with the teams to refine an idea - is 'invisible'. So CD's are often tempted to write stuff themselves, to 'prove their worth'.

Now comes the tricky part. I've been careful to say up to now that I don't think CD's should 'write ads', by which I mean they shouldn't do the whole thing. But that doesn't mean CD's shouldn't have ideas. They should. Hundreds of them. 

Firstly, they should be working collaboratively with the strategists to come up with ideas around what the brief should be. (You may be surprised to hear that many CD's put virtually zero effort into the brief, feeling that it's 'not their job'. Bullshit. Working with the strategists to get to a great brief should be a huge part of their job).

And secondly, they should be working collaboratively with the creative teams (in fact, the whole agency) to get to great ideas. That could mean throwing out an interesting 'half-idea' that the creatives can build on, or it could mean finding a way to turn a half-thought of someone else's into something great.

So in summary, a good CD never 'writes ads', but instead comes up with hundreds of half-ideas. And takes zero credit for them. Sounds tough, but that's the job as I see it.