One of the things that really interested and saddened me in reading and thinking about the whole annihilationism / eternal conscious torment debate was the extent to which it often shows the truth of 2 Timothy 2:14.
Warn them before God against quarreling about words; it is of no value, and only ruins those who listen.
A large portion of the debate consists in arguments over two (or three) groups of words - the words translated into English as "destroy" or "destruction" (two groups in Greek) and "eternal". In both cases, the arguments show something interesting, but in neither case do they show what the people using them want them to show. Which makes me wonder why people keep using those arguments - it's almost as if they've made their minds up and then try to find evidence to back up their decision...
The Meaning of "Eternal"
The Greek word translated "eternal" is aionios, and it is often used as an argument that there is eternal conscious torment. However, as Fudge points out in his book "The Fire that Consumes", it might mean "eternal in effect" rather than just "eternal in duration". It seems clear that the description of what happens to the unsaved as "eternal" means that it doesn't end - that Hell isn't like Purgatory in the medieval Catholic doctrine. But it isn't clear from that word whether Hell is somewhere people go and stay forever, or whether it's a sentence of extinction which lasts forever.
The Meaning of "Destruction"
The other word group that gets cited a lot on the other side of the debate is the idea of "destruction", which is used to describe what happens to the unsaved after death. There are three words used in Greek - apollumi, apoleia and olethros.
Apollumi means "destroy", but the meaning in Greek is much broader than in English. For example, it is also used of the lost coin, sheep and son in Luke 15. Apoleia is also used to mean "wasted", like the perfume in Mark 14:4, and olethros is used a lot in the Old Testament to mean "cut off".
So the word "destroy" doesn't mean that the unsaved are annihilated. It does mean they are changed, or ruined, but doesn't necessarily imply annihilation.