Against "the ending of a sentence or clause with a preposition", that is.
Chris Waigl wrote from Paris to point this out, in response to Starcreator's suggestion that we should "look, simply, to the French" so as to "see how things are supposed to be done" with respect to clause-final prepositions.
Chris observes that
...if the argument is entirely deleted from the clause (and retrieved from the context), and also in a few other cases where the argument is fronted, some prepositions end up stranded in standard spoken French.
She offers an example from a speech by Victor Hugo:
"Ici, messieurs, quand j'approfondis ce vaste ensemble, ce vaste concours d'efforts et d'événements, tous marqués du doigt de Dieu; quand je songe à ce but magnifique, le bien-être des hommes, la paix; quand je considère ce que la providence fait pour et ce que la politique fait contre, une réflexion douloureuse s'offre à mon esprit." [emphasis added]
"Here, gentlement, when I examine in detail this vast collection, this vast coincidence of efforts and events, all marked with the hand of God; when I dream of this marvelous goal, the well-being of mankind, peace; when I consider what Providence does for [it] and what politics does against [it], painful thoughts fill my mind."
And another from Emile Zola's Germinal:
"Quand on savait s'y prendre, un logeur devenait une excellente affaire. Seulement, il ne fallait pas coucher avec."
"When you know how to manage one, a lodger could be a good thing. Only, you mustn't sleep with [them]."
Chris also offered some "random samples of informal writing", taken from the web. [The English translations thoughout this post are mine -- Chris would have done a better job. The clause-final prepositions are signaled by bold italics, and a bit of orthographic hygiene has been performed here and there.]
"Je lui avais dit oui pour sortir avec mais j'aurais jamais dû."
"I told him yes for going out with [him] but I shouldn't have.""Sortir avec et se marier, c'est pas la même chose."
"Going out with [someone] and marrying [them], it's not the same thing.""Je me garderais bien de dire si il s'agit de la verité ou juste d'une sorte de fantasme de Catherine Allegret qui somme toute pourrait fort bien être l'une des rares femmes à avoir côtoyé Montand sans avoir couché avec et qui en ressentirait une sorte de jalousie."
"I'd be careful not to say whether it's the truth or just a sort of fantasy of Catherine Allegret who in the end could well be one of the rare women to have been around Montand without having slept with [him] and who therefore felt a sort of jealousy.""Il faut choisir un bijou vraiment fait pour cet endroit et pas prendre un piercing nez comme on me l'avait conseillé, ils ne sont pas faits pour et du coup se prennent souvent dans les cheveux."
"You should choose an ornament really made for that location, and not just take a nose piercing as someone suggested to me, they're not made for [that] and often suddenly catch in your hair.""Quelque temps plus tard ils voient deux hommes monter dans la voiture et partir avec."
"Some time later they saw two men get into the car and leave with [it].""Voilà donc, au diable les règles, elles ne sont jamais faites que pour ceux qui ne savent pas vivre sans."
"OK then, to hell with the rules, they're only made for those who don't know how to live without [them].""C'est moi qui lui ai couru après."
"I'm the one who ran after her/him."
Word-for-word: /it is me who her have run after/.
("courir après <quelqu'un>" is a special case and particularly flexible; lots of stranded prepositions)
Chris observes that
This is all perfectly grammatical and extremely common.
As far as I can tell, this works for _avec_, _pour_, _contre_, _sans_, _après_ .... It doesn't for _à_ and _de_ (they get absorbed into the pronouns _y/lui_ and _en_ when their argument is deleted), nor for _sous_, _sur_ or _dans_ (they transform into the adverbs _dessous_, _dessus_ and _dedans_, which anaphorically link back to the argument of the preposition).
There are a lot of other prepositions that can also function as adverbs (_devant_, _derrière_), for which I'd have to find out which category the stranded word belongs to before going any further. And for some it doesn't work and I don't know why (_par_, _en_, _jusque_...).
It's important to keep in mind that all this is separate from the stranding of prepositions at the end of relative clauses, which is allowed in some varieties of Canadian French (and maybe here and there in varieties of continental French? I don't know). See these Language Log posts for more:
Quoi ce-qu'elle a parlé about?
More on Canadian French preposition stranding
And I can't resist ending with this characteristically American take on grammatical correctness:
Posted by Mark Liberman at June 30, 2005 07:54 AM