Arnold Zwicky’s got a great post over on Language Log about at about, as in:

(1) I ate a tuna and jellybean sandwich at about 4:15.

Basically, a bunch of prescriptivists have a pet peeve that at about is redundant because you’re “piling up” prepositions. It isn’t at all. First, look at these sentences without one of the prepositions:

(2)a. I ate a tuna and jellybean sandwich at 4:15.
(2)b. I ate a tuna and jellybean sandwich about 4:15.

(2)a does not mean the same thing as (1) – it might be that you had an alarm clock go off at precisely 4:15, flipped through your agenda, and found a note saying “EAT TUNA/JELLYBEAN SWICH”, and pulled one out of the fridge. And (2)b, to me, sounds tremendously colloquial – I would not write this in a paper, although I would without hesitation write (1). The prescriptivists argue that Omit Needless Words kicks in here and thus you’ve got to ditch one of the prepositions, but it’s plain to see that omitting a preposition changes the meaning or tone of the sentence: neither preposition is needless!

Zwicky makes a really important point that needs to be kept in mind by all grammarians: members of the same syntactic category (i.e., prepositions) can have different grammatical functions. With at about, at‘s syntactic function is as an operator, whereas about‘s function is as an adverbial. Piling up prepositions is commonplace (Zwicky cites numerous examples of unquestionably grammatical at about strings); what prescriptivists mean to complain about is piling up words of the same syntactic function, as in:

(3) Unsurprisingly, I ate a another tuna and jellybean around about 4:25.

I intend to remain agnostic about sentence (3); it is possibly better to only use around or about, because they both have an adverbial function, and they both have approximately the same meaning in that function.  The take-home point here is that when you’re trying to argue about language with something like Omit Needless Words, you’ve got to be sure that the words are truly needless, and are needless for a principled reason.  (Even then, ONW will lead you astray – I hope to blog about some new research on this point soon.)  As Zwicky puts it, the prescriptivists’ unstated rule is:

“Follow this advice, unless that would be wrong.”