What's With This 'Great and Terrible Day of the Lord'?

One thing in the gospels that is most definitely historical, the first fact after 'He got born somehow' is this: John the Baptist was down by the Jordan dressed like Elijah and stirring up spectacular trouble.

Why dressed like Elijah, living like Elijah in the wilderness? Does John feel that 'the spirit of Elijah' is at work in him? Later rabbis (among the Hasidim at least) reported definite experiences indicating that they remembered previous incarnations, and accepted these as part of the tradition -- Part of the tradition going back how far? Do we know? Since Elijah's story ends with him departing in a flaming chariot, Elijah was the Biblical figure most commonly expected to return bodily. Indeed, Malachi ends with a direct prediction of such a return: [Malachi 3.13->]

"Your words have been stout against me," says the Lord. "Yet you say, 'How have we spoken against Thee?' You have said, 'It is useless to serve God. What is the good of our keeping His charge or of walking as in mourning before the Lord of Hosts? Henceforth we deem the arrogant blessed; evildoers not only prosper but when they put God to the test they escape.'"

Then those who feared the Lord spoke with one another; the Lord heeded and heard them, and a book of remembrance was written before Him of those who feared the Lord and thought on His name.

"They shall be Mine," says the Lord of Hosts, "My special possession on the day when I act. And I will spare them as a man spares his son who serves him. Then once more you shall distinguish between the righteous and the wicked, between one who serves God and one who does not serve Him.

"For behold, the day comes, burning like an oven, when all the arrogant and all evildoers will be stubble; the day that comes shall burn them up," says the Lord of Hosts, "so that it will leave them neither root nor branch. But for you who fear My name the sun of righteousness shall rise, with healing in its wings. You shall go forth leaping like calves from the stall. And you shall tread down the wicked, for they will be ashes under the soles of your feet, on the day when I act," says the Lord of Hosts.

"Remember the law of my servant Moses, the statutes and ordinances that I commanded him at Horeb for all Israel.

"Behold, I will send you Elijah the prophet before the great and terrible day of the Lord comes. And he will turn the hearts of fathers to their children and the hearts of children to their fathers, lest I come and smite the land with a curse."

Jesus says somewhere that ~'John was Elijah, if you want to think of it that way.' John himself seems to believe he is fulfilling that role. But is he foreshadowing a Day that came several decades later, with the fall of the Temple? Did that burn up all the evil in the world? Aren't we still forced to say (even though much of the time we find nice, well-intentioned people -- even us ourselves -- acting as inadvertent accomplices) that not only do evildoers prosper but that they tempt God and (to all appearances) escape? Was that The Day that was promised, or should we look for another? And what are we supposed to expect this to mean?