Preposition, final.

It is a widely held belief that it is incorrect, unorthodox, or simply dispreferred to use sentences with prepositions in final positions in literary or written English. This is a misplaced belief. Geoff Pullum points out that it all starts in 1672 with an essay by John Dryden, titled "Defence of the epilogue", in which the author enumerates a series of examples of unorthodox writing in several contemporary authors' works. One of such mistakes was indeed to have a "Preposition in the end of the sentence". There are many criteria to establish that this is a made up canon. First of all clarity and conciseness. As the guys over at Language Log noticed, the On-Line New Yorker article search engine, when stumbling upon a search that returns no results, warns the user with the following message:

??I'm sorry I couldn't find that for which you were looking.

Compare this with the more natural,

I'm sorry I couldn't find what you were looking for.

As it should appear evident, the second form is more natural, clearer and more concise. If anything, to conform to a more ltiterary style, the contracted verbs could appear in their standard, non abbreviated form (I am / I could not).

The second issue here is that to look for with the meaning of to search or to seek is really not a generic verb supported by a prepositional complement. This would be the case of sharing a room with somebody, for example. In such cases, separating verbs from the prepositional complement is not nearly as bad to the ear as it is in the case of a phrasal verb, such as to look for. The sentence

That's not the man with whom I shared the room.

is much better than the above example. Still, That's not the man I shared a room with is just as clear, and slightly more concise (7 words against 8).

The interesting thing is that the English language - at least when compared with other languages, or cultures associated with other languages - has always had less of a prescriptivist character tied to it. Italy and France for example, still today have institutions dutybound to protect their languages and charged with the task of dictating their correct and standard usage. The OED - arguably the most authoritative source of information on history and usage of the English language - has always prided itself of its descriptivist approach to documenting the evolution and extent of the English idiom. It is nontheless curious that so many have fallen prey to the rants of a single, opinionated man. And HE didn't even have a blog as a pulpit.