In my recent essay on Hell, despite the fact that a lot of the arguments are inconclusive, I ended up concluding that annihilationism (the belief that those who aren't saved eventually cease to exist) probably doesn't fit with what the Bible says. This is why.
John Wenham, a noted annihilationist, says that Revelation 14:9-11 is “the most difficult passage” for his point of view. It's also very hard-hitting.
And another angel, a third, followed them, saying with a loud voice, "If anyone worships the beast and its image and receives a mark on his forehead or on his hand, he also will drink the wine of God's wrath, poured full strength into the cup of his anger, and he will be tormented with fire and sulfur in the presence of the holy angels and in the presence of the Lamb. And the smoke of their torment goes up forever and ever, and they have no rest, day or night, these worshippers of the beast and its image, and whoever receives the mark of its name."
Revelation 14:9-11, ESV
Lots of scholars, particularly annihilationists, link the smoke going up for ever to the destruction of Edom in Isaiah 34:9-10. Greg Beale, who wrote quite possibly the best commentary on Revelation summarises:
The image of continually ascending smoke in Isaiah 34 serves as a memorial of God's annihilating punishment for sin, the message of which never goes out of date... Therefore, the imagery of Rev. 14:10-11 could indicate a great judgement that will be remembered forever, not one that leads to eternal suffering.
However, Beale eventually rejects this point of view on the grounds of the parallels with Revelation 20:10, where there is clearly everlasting conscious torment, at least for Satan (see later), and because of the “torment” - the word is basanismos, which is never used of annihilation.
Therefore ... “the smoke of torment” is a mixed metaphor, with “smoke” figurative of an enduring memorial of God's punishment involving a real, ongoing, eternal, conscious torment.
It is not the smoke of a completed destruction, but “smoke of their torment.” The nature of the torment is explained in the second part of v11: it is not annihilation but lack of rest.
I honestly cannot see a way of reading Revelation 14:9-11 in its entirety which is compatible with annihilationism. Some people (e.g. Fudge) note the smoke rising forever, but don't really consider the fact that it's the smoke of their torment. Others (e.g. Powys) see Revelation 14:9-11 as a hypothetical threat for those who go back on their belief in Jesus, but which God would never actually carry out. I cannot find anyone who comes up with a credible interpretation of this passage which doesn't involve some form of eternal conscious tormented existence for at least some of the unsaved.
The other really important passage here is the idea of the Lake of Fire in Revelation 19-21.
and the devil who had deceived them was thrown into the lake of fire and sulfur where the beast and the false prophet were, and they will be tormented day and night forever and ever.
Revelation 20:10, ESV
Gomes writes of this:
By juxtaposing the words “day and night” with “for ever and ever” in 20:10, we have the most emphatic expression of unending ceaseless activity possible in the Greek language.
Even Fudge admits that this seems to be everlasting conscious torment, though he argues that while the lake of fire torments the devil, for people, the lake of fire is annihilation, basing this on its description as the “second death” (20:14, 21:8). He argues that the Beast is an abstraction, though fails to describe what it means for an abstraction to be tormented “day and night, forever and ever.” However, as Pawson points out, it seems that at least one human – the False Prophet – does indeed suffer everlasting conscious torment.
Also thrown into the Lake of Fire are Death and Hades (20:14), anyone whose name is not written in the Book of Life (20:15) and various groups of sinners who are excluded from the New Jerusalem (21:8). It also seems that Fudge's argument that the Lake of Fire is immediate annihilation does not work. The Beast and the False Prophet are thrown into the Lake of Fire in Revelation 19:20, and are still there in 20:10, where they are joined by the devil and will be tortured for ever. Those who are excluded from the New Jerusalem and the Book of Life are thrown in in 20:15. In Revelation 21:8, we are told that their “part” will be in the lake of fire. And in Revelation 22:15, they still seem to exist, simply “outside”.
Although we need to be careful when drawing concrete conclusions from a book which uses language in such a non-concrete way, it does indeed seem that Revelation teaches some form of continued existence for the unsaved, even some form of eternal conscious torment.
Oh, and the other solid argument is that almost no-one is on record as believing annihilationism from AD 150 to 1650. As doctrines go, it looks like a late innovation to me...