My understanding (and forgive me if I'm wrong; this is 25-year-old information) is that, in proper English, a prepositional phrase begins with its preposition; the words that follow the preposition are thus dependent upon it, and keeping it in that order makes the meaning of the phrase clearer.
Improper usage tends to take two forms:
1) Leaving off the remainder of the phrase. For example: "I'm going to the store, do you want to come with?" ("me" is implied, and the gramatically-correct ending of that sentence is "do you want to come with me?")
2) Inversion of the preposition with its dependent phrase. For example: "Never use a preposition to end a sentence with." (Gramatically-correct version is, "Never end a sentence with a preposition.")
My suspicion is that the gramatically-correct versions sound overly-formal to many people, even if they know the rules. Common usage of dangling participles seems to have really increased in my lifetime; I wouldn't be suprised if it eventually becomes "acceptable" (that's how language changes).