These days,
civil disobedience is usually done in the form of a
public protest among several people. It works best with acts that are (apparently)
victimless crimes; if 100 people protest the
war on drugs by selling
crack on the steps on the
capitol, they are not going to get much
support.
Acts of civil disobedience need not be related to the law that is being protested...note that Thoreau didn't object to the poll tax per se, but he refused to pay as a way of protesting slavery.
The Man has gotten wise to acts of civil disobedience, and is sometimes canny enough to know when not to play along. For instance, police in Madison, WI might spend their day at the Weedstock event on the sidelines maintaining order, make a note of who is seen in posession, then quietly bust them at a later (and less public) time.