it's called "target" marketing for a reason

Right.

Could someone please explain to me what, exactly, the McDonald's corporation expects to accomplish by creating I Am Asian.com?

Two things immediately come to mind. One, do people actually buy this crap? Do people of the particular target market at which a given ad is aimed actually see it and go "Hey, McDonald's is cool, like me! They know what I'm about! They understand my culture! I should eat there, like a good little [insert ethnicity here]"? I somehow doubt it. While I'm often guilty of wondering just how stupid people can be, I seriously doubt anyone is THAT stupid. Seriously. (And I hope I'm not proven wrong on this point, though I fear I shall be, having stated it like this. XD)

Two, when you reach the sort of saturation level of a multinational corporation such as McDonald's, do you even NEED to advertise anymore? It's to the point where McDonald's is nearly synonymous in international minds and across language barriers with "fast food." As to what that "fast food" actually entails, your mileage will of course vary by region, country, and etc., but it's a lot like the term "photocopy" often being replaced by "Xerox" in normal speech. Or "tissue" being replaced by "Kleenex." These brands have transcended association with a brand of an item and have come instead to be understood as synonymous with all instances of that item, whether you actually photocopy your documents on a Xerox-brand photocopier or a Toshiba, or whether you blow your nose with Kleenex, Puffs, or your local generic equivalent.

When you reach that point in your growth as a hideously oversized behemoth of a corporation, what is the POINT? I mean, other than showing how grossly out of touch you are and pissing off as many of your potential customers* as you can?

At what point does overadvertising become counterproductive, regardless of stupidity of content? Do ad agencies actually ever believe it does?

I think I've reached the point where it's really their utter cluelessness in their blatant shilling efforts that's most primarily offensive. :P

* = Apart from the ones who would already be pissed off because they've Done Reading About You and have some sort of social conscience dictating the direction of their anger?