... continued from yesterday
A couple features of this issue have caused great discussion over the years. One is the question of the unpardonable sin. When Jesus' opponents suggest he performed miracles by the power of Satan, Jesus warns them starkly. Attributing the work of the Holy Spirit to Satan is serious business, a sin that will not be forgiven.
Many a sensitive soul has struggled with this concept in self-doubt. Have I committed this sin? I heard of a man once who participated more faithfully in a church than anyone else and yet was convinced there was no hope for him. In his mind he had committed the sin from which no one can return.
In that light, a bottom line is in order. If it is the Holy Spirit that draws us to God in the first place, then anyone who truly is seeking God cannot have committed such a sin. In other words, anyone who has committed this sin will not want to come back to God. If you are truly seeking God, you are good to go.
Of course what does it mean to seek God truly? Many a child is sorry she got caught rather than truly remorseful for doing something bad. Perhaps it is not exactly what Hebrews 12:17 means, but the wording is interesting when it says that Esau, "found no place for repentance, though he sought for it with tears" (NASB). A truly repentant heart is something deeper that realizing you're in trouble.
But the person who thinks God is always hiding around the corner, waiting to give you a "sinning ticket," has a false picture of God. God is standing out in the open, looking for any chance to reconcile and welcome you. The other picture is unhealthy and often leads us to pass on legalistic judgment to others as well.
The take-away from the unpardonable sin is for us to be careful not to miss the working of the Spirit in others. For example, for years many people in my church wondered if those who spoke in tongues were demon-possessed. I hope that for most it was a sincere question rather than an accusation. Why even take a chance on such a thing? If speaking in tongues can be from the Holy Spirit, then attributing it to Satan is very similar to the unpardonable sin of Mark 3:28-29. 
In general, we should be very careful about judging others (Matt. 7:1) or assuming that God can't work in others in ways he doesn't work with us. It's not just that it is the wrong attitude on our part. It's that we ourselves may miss out on a blessing by way of others.
Another issue raised by Jesus' healing of the paralytic in Mark 2 is the authority to forgive sins...
 There is of course a third option, that some speaking of tongues can be a psychological phenomenon that some human brains are wired for. In fact, the gift of tongues could be the Holy Spirit blessing individuals with this sort of wiring. This would explain why we sometimes find tongues-speaking in other religions.