Brush the dust from your feet vs cursing a town Is brushing the dust from your feet when you leave an area the same as putting a curse on it?
Jesus said this to his disciples prior to sending them out:


  If anyone will not welcome you or listen to your words, shake the dust off your feet when you leave that home or town.  I tell you the truth, it will be more bearable for Sodom and Gomorrah on the day of judgment than for that town (Matthew 10:14-15)


My NIV Study Bible makes this comment:


  A symbolic act practised by the Pharisees when they left an “unclean” Gentile area.  Here [in Matthew 10:14] it represented an act of solemn warning to those who rejected God’s message.


It seems that the Pharisees had a tradition of shaking the dust off their feet when leaving an unclean place.  There is a similar event recorded in Luke 9:5:


  “If people do not welcome you, shake the dust off your feet when you leave their town, as a testimony against them.”


My NIV Study Bible makes this comment:


  A sign of repudiation for their rejection of God’s message and a gesture showing separation from everything associated with the place.


Another example is when Paul and Barnabas left Pisidian Antioch.  They shook the dust from their feet in protest against the Jewish community  who had stirred up persecution against them and who expelled them from their region (Acts 13:50-51). My NIV Study Bible makes this comment:


  Paul and Barnabas did this to show the severance of responsibility and the repudiation of those who had rejected their message and had brought suffering to the servants of the Lord.


By rejecting Jesus’ messengers, who proclaimed the nearness of the Kingdom of God, the people of that town were effectively rejecting the gospel message, and so they would have to answer to God for their unbelief. However, Paul and Barnabas did not place a curse on the towns from which they had been forcibly ejected. They came back to continue preaching the gospel, which was received by the Gentiles in those places, and they established churches and appointed elders.