English is normally a subject-verb-object kind of language, but there are some interesting exceptions, especially in casual contexts. Consider examples such as the following:
Poodles, we walk them. Labradors, they walk us.
Chickens we have; roads, not so much.
Not one of the clauses above follows standard English sentence order, and yet we understand them. Of the four clauses, the first is object, subject-verb-object (pronoun); the second is subject, subject (pronoun)-verb-object; the third is object-subject-verb; and the fourth is object, adverb — no subject or verb overtly expressed at all. All four are examples of topic fronting, sometimes called left dislocation. (Note that we normally use a comma to set off the topic when it’s followed by a complete clause or an elliptical statement, but not usually when the sentence is not syntactically complete without it.)
So why do we depart from our usual syntactic structure? We do it to maintain our preferred information structure. When we communicate information, we usually prefer to introduce a topic and then comment on it with new information. This can be especially useful when we’re contrasting two topics. We don’t have to do it; we could rewrite the above sentences as follows:
We walk poodles. Labradors walk us.
We have chickens; we don’t have roads to nearly the same extent.
The first example works well rewritten, though it loses its folksy feel; it also loses the parallelism of topics, but it highlights the inversion, which has its own effect. The second really, um, fails to cross the road. And even in a structure such as the first, you get poorer results if you can’t make a useful inversion:
Shirts, we mend them. Shorts, we toss them.
We mend shirts. We toss shorts.
You can see it loses some of the contrast effect. In speech you can emphasize the topic structure using intonation; in print that option is not as available.
Now look at the preceding sentence “In speech…”: it contrasts the adverbial prepositional phrases thematically by moving them from the end to the beginning of their clauses — and no one would object to it. So why does it seem somehow incorrect to do it with nouns?
It’s not because it’s some new error, or a structure borrowed from another language (though some languages do normally introduce topics first, regardless of syntactic role). In fact, as Mark Liberman has discussed on Language Log, left dislocation has existed in English as long as there has been an English for it to exist in.
What has happened is that it has fallen out of use in recent centuries. Like some other formerly standard things, such as double negatives, double superlatives, use of ain’t, pronunciation of –ing as –in, and use of ’em in place of them, it has come to be seen as nonstandard, especially when there’s also a pronoun filling the same role — we can sometimes get away with it as poetic when there is no pronoun:
Parsley we put on the plate, sage we leave on the plain,
rosemary and thyme we drop in the pot.
The nonstandard air of left dislocation is a useful means of making your text seem casual or colloquial, and also keeps a nice clear parallelism. On the other hand, if you need to seem more formally correct, you still have a means of putting it in front acceptably: just turn the parallel nouns into parallel prepositional phrases:
With poodles, we walk them; with Labradors, they walk us.