Second of all, you cannot entirely ban TNT as an item, there are always ways around. (= inventory hacks)
Just remove it from the inventory then. Once check per second should be sufficient.
and finally, TNT is being prevented from detonation, but the intent to detonate it alone shows me that someone just doesn't get it if I repeat 30000x not to use TNT. And if one can't comprehend that, or doesn't want to. It shows me that he/she is probably not a team player or a rule-follower, and I don't want that kind of person on my server.
Or it was a simple mistake. Since no harm was caused whatsoever (maybe he used it for mining?) its just silly to ban someone for trying.
Oh, and it wouldnt be too hard to just write a plugin that logs TNT placement and its owner. Either do it via an external array or just use some of the unused bytes.
