What I want to know is…
who the hell ever decided that a preposition must have an object and other such rules for the English language?
how did they decide that?
and what gave them the authority?
Don’t get me wrong, I love the preposition rule and all, I just want to know how it came about.
There is no “International Tribunal of Grammar”. There are several sources for the rules- and they can be broken down to: “their own stinken opinion”, and ‘common usage". When the gammar mayen try to promote, or more likely stop, something which is in "common usage’- they are acting against the natural evolution of the language, not to mention being bossy, meddling assholes.
I just wanted to add another question to this. On another (one of many) grammer/language thread, somebody posted that the “rule” that a preposition may not end a sentence has no grammatical basis in either British or American English, and that it is instead a throwback to a Latin (IIRC) rule that a preposition may not come at the end of a sentence. Does anybody have any evidence to (dis)prove this point?
KKB: the Oxford Companion to the English Grammar, their usage book, more or less agree with you. The 'rule" comes from latin (& greek). To quote: “However, although English propositions often do precede their complement, there are structures in which this is impossible”. Oxford thus accepts, as standard usage, and proper grammar- a sentence ending in a Prop, when the alternative is stilted or hard to understand.
The language existed for centuries before anyone came up with rules about it. In fact, any native speaker does know the rules – they just can’t articulate what the rules are (in other words, they know “I are a writer” is wrong, even if they can’t explain why).
The rule against ending a sentence with a preposition (as well as the rule agains splitting infinitives) were developed in the 19th century, when it was felt by scholars that Latin was the ideal language and that English should aspire to Latin. Since there is a “pre-” in “preposition,” they decreed that it has to come before another word, so ending a sentence with one was Bad.* The stricture against splitting infinitives was set because infinitives in Latin are one word, not two as in English, and were thus unsplittable. Most grammar experts these days don’t consider these hard-and-fast rules and just say don’t do it if it makes the sentence awkward.
*Technically, you rarely end a sentence with a preposition in any case. What people consider prepositions are actually particles – the second (or third) part of a multiple-word verb. Thus the verb “to throw up” is one construction, meaning “to vomit.” Thus, “He threw up” does not end in a preposition, but merely with the particles of a phrasal verb.
This is the sort of utter nonsense up with which no one should have to put. 
I, personally, often end a sentence with a proposition, sometimes even an indecent one.