Opiniatrety

Sounds okay to me. Wh-movement is generally grammatical; it's the few situations where it isn't that syntacticians are always talking about.

Yeah, those few situations are what I don't understand (I tried to read Chomsky's Barriers and had no luck). This sentence seems so convoluted that I'm unclear about it, but I guess it's OK.

That sentence is just parallel to:

What did you say was your favorite flavor of ice cream?

At least, the wh- movement is coming out of the same sort of place, but the phrases around it are larger. There's apparently some linguists that argue that certain constraints really are quantitative, so that things get degrees of grammaticality. I think this is based on work from phonology initially though.

The place that seems to be ungrammatical is moving both the subject and object of the same sentence:

*That's the book that I don't know what is called.
?That's the book that I don't know what it's called.

What few situations don't you understand? Just kidding.
An editor's view, instinctual, rather than a linguist's view:
I would have edited it to "What plan was likely doomed to fail, according to a top expert's warning to the ISG?" or "One top expert warned the ISG that a certain plan was doomed to fail. Which [or "what"] plan?"
Wikipedia has a pretty thorough discussion of wh- movement (or "mouvement q" in French), which I'd never heard of before.
(What had she never heard of according to her own report before?)

I tried to link to that wikipedia entry last night, but was foiled by the spam filter.

Here's yer link. I think what gets me is the length of the moved wh-phrase, and the additional wh-phrase; the sentence seems grammatical but unnecessarily convoluted.

Haven't any of you people ever watched Jeopardy?