From Gail Collins’s op-ed column in the NYT yesterday, “A Ted Cruz On Every Corner”, about recent looniness from Texas lawmakers:
The old center-right standard-bearer, Lt. Gov. David Dewhurst, is desperately trying to wipe out his reputation as a mainstream politician while he runs for re-election.
“I don’t know about you, but Barack Obama ought to be impeached,” he told a Tea Party gathering recently, with more fervor for the cause than for grammatical construction.
Collins doesn’t explain her objection, but I’m guessing she thinks that Dewhurst should have said:
“I don’t know about you, but I think Barack Obama ought to be impeached.”
(supplying the source of the opinion in the second clause). So she’s treating this case as (roughly) parallel to the truncation of as far as X goes / is concerned to just as far as, which has been widely reviled (for reasons I don’t fully understand).
On as far as, see this posting, where it’s contrasted with various no matter truncations (which seem to elicit no negative press).
I don’t know about you, but (without I think) is enormously frequent — in raw ghits, 109.2m without it to 28.2m with I think — and it’s recognized in the Cambridge Advanced Learner’s Dictionary & Thesaurus as an informal construction
used to mean ‘whatever you are going to do’ or ‘whatever you think': I don’t know about you, but I’m going to bed.
So: the construction is (at least from the historical point of view) truncated and it’s informal — but that doesn’t make it ungrammatical.
What’s interesting in this in that Collins is a master of informal style (including strategic deployment of slang) in her writing, even in this very posting.