A ban on landmines is unenforceable because any country that decides to go to war and/or to use landmines is going to be determined to be rogue and there not beholden to any form of treaty. Also the enforcement of such a ban brings about its own problems such as funding and use of troops or monitors.
Looking back at the history of the United States, treaties have often been useful and beneficial to make, but are certainly not always followed through. When it comes down to it, the interest of the state will always trump an agreement the state makes with another body. For example, the US government broke over 500 treaties made with American Indian tribes in its time when the treaties proved to be not beneficial to the country.
I see nothing wrong with landmines. They are nothing more than tools used by the army. I've read about some battles that used landmines, and they greatly slowed the enemy because they were EVERYWHERE! This gave the soldiers plenty of time to prepare, and they easily on the battle. Nukes, however, are a different story, and I think they SHOULD be banned from all countries. Forever.