edit: http://penny-arcade.com/patv/episode/mass-effect-3-dlc
I disagree with this for a few fundamental reasons. first of all, while it may be true that developers may not likely sell as many DLC several weeks or even months after the core game is released for purchase. It reduces the chances that cheap and poor quality DLC will be made and sold. As cheap and frivolous DLC simply will not sell because such a product depends solely upon the hype of the game newly being released.
Which is to say that a quality product will create a demand to purchase the product, while DLC made poor for nothing more than a low production cash grab will be ignored because the new game hype is gone.
Bethesda for example, they spend several weeks if not months developing their DLC (with the exception of some, IE; horse armor.) which so far for them has not only been significant successes but also added significant game play to the core title over all. So much so that those DLC/Expansions are considered to be as much as part of the whole tittle rather than a simple add on sale.
Secondly. The fact that day one DLC can be abused, means that it is guaranteed to be abused. Murphy's law would support this argument. Although not simply because it can happen, but more so because it is aligned with lucrative incintive as well as human nature (specifically greed).
Developers may not develop cheap and virtually nil quality day one DLC with the specific intention to cause despair. However when there is an economic insentive people will find all kinds of ways to justify to themselves that wrong decisions are part of an exception, or even simply a part of business.