Identity of Christ's Bride I've always believed (like Christians around me) that Christ's Bride is the church. However, I recently met two guys that claimed that the Bride is actually the new Jerusalem that comes down from Heaven in Revelation (3:12, 21:2, 21:10). What is the Biblical support for these two viewpoints?
The new Jerusalem that comes from heaven in Rev 19 is "prepared as a bride adorned for her husband." (emphasis added) However, I would understand why some might think that Jerusalem is Christ's bride. In the Old Testament, Israel (or Judah or Jerusalem) is described as God's wife:


  For thy Maker is thine husband; the LORD of hosts is his name; and
  thy Redeemer the Holy One of Israel; The God of the whole earth shall
  he be called. For the LORD hath called thee as a woman forsaken and
  grieved in spirit, and a wife of youth, when thou wast refused, saith
  thy God.
  Isa. 54:5-6
  
  Turn, O backsliding children, saith the LORD; for I am married unto
  you: and I will take you one of a city, and two of a family, and I
  will bring you to Zion:
  Jeremiah 3:14


This comparison is the whole purpose of the book of Haggai as well. It's a beautiful way to render God's relationship with his people.

Contrastingly, the imagery that we have with Christ and His Bride is that of a coming Bridegroom and a bride in preparation. As the angel shouts in Revelation 19:7


  "Let us be glad and rejoice and give Him glory, for the marriage of
  the Lamb has come, and His wife has made herself ready."


Paul strengthens this image when he says in II Corinthians 11:2


  ...I am jealous over you with godly jealousy: for I have espoused you
  to one husband, that I may present you as a chaste virgin to Christ.


The two metaphors are not contradictory. Jesus uses many contrasting "I ams:" Jesus is the Lamb, the Door, The Good Shepherd, etc. All of them are helpful, but they are only pictures. HOWEVER, this imagery of Christ and His bride persists through all the New Testament, especially in the Revelation. It is meant to typify how an engaged virgin would wait for her promised husband to come for her. That is what Christians are doing today. God was never married to a city. Jesus is not coming back for a city. The city always was a symbol for the collective people of the city, and the Bride is a metaphor for all the Christ's body.