JI Packer writes of the demons that their activity was uniquely intense during Christ's earthly ministry, something that charismatics today miss. He also says that exorcism is occasionally still needed - that the Lutheran abolishment of it in the 1500s was premature (Concise Theology, pg 68). This conflicts with the idea I've also heard that true believers cannot be possessed. I'm not too sure which way to go on this one, but lean toward Packer's position. Satan is stronger than us, and God often allows even believers to fall into serious and prolonged sin, under the influence of the world or demons. There are credible, quiet reports of demon possession and exorcism out there, aside from all the charismatic hype. I don't recall the Scripture used for the other position, but it is an inference to an absolute position, which isn't as conclusive.