Mark chapter 4 begins much like chapter 3, by describing that Jesus must speak to the crowd from a boat to keep from getting trampled to death (3:9). We can envision a scene much like what happen at Wal-Mart a few years ago, when a person was killed because of the madness of the crowd trying to get a good deal on Black Friday. The big difference is that in the Bible story, it is the Son of God that people had no regard for, they would trample Jesus Christ to fulfill their own selfish desires.
In contrast to the selfish crowd are the disciples that followed Christ more for what they saw in Him than what He could do for them. Mark begins to clarify these two groups of people in chapter 4 by distinguishing between those that Jesus spoke to only in parables and those to whom He explained them (Mark 4:34). Friends make themselves known to each other, Jesus is Lord but He becomes a friend to those who believe in Him (John 15:15). Jesus discloses His will to His friends, but to those who hate, reject, and/or simply ignore Him He speaks in parables.
The first distinguishing mark of a true Christian is their ability to understand the doctrines or teachings of Christ as revealed in the Bible (1 Corinthians 2:10-13). Christians are built up in the faith as they receive truths that are only made available to them, and the division grows as they begin to think differently from the world. Christian theology is in stark contrast to the thinking of the world; namely that the Christian is one who loves Christ more and more each day, while the people governed by the thinking of the world constantly reject the teachings of Christ. The morality of the Bible is scorned by our present cultural standards.
Jesus taught His disciples the distinct difference between true and false converts, and He taught them about accountability in the local church (Matthew 18:15-17). Of course love is the governing principle, but it is not loving to allow a person to believe himself in the kingdom of God if in fact he is not.
If the church is to remain pure and holy their must be an accounting of true discipleship; the one who follows Christ only for what he can get from Him is not a true disciple. Mark records in chapter 4 that Jesus taught the Parable of the Sower, in which some seeds fell upon bad soil and they did not bring forth fruit. Those that fell upon good soil represent the saved because they bring forth fruit; bad soil cannot bring forth fruit because its increase is not from God.