From the Bible:

21 After saying these things, Jesus was troubled in his spirit, and testified, “Truly, truly, I say to you, one of you will betray me.” 22 The disciples looked at one another, uncertain of whom he spoke. 23 One of his disciples, whom Jesus loved, was reclining at table at Jesus’ side, 24 so Simon Peter motioned to him to ask Jesus of whom he was speaking. 25 So that disciple, leaning back against Jesus, said to him, “Lord, who is it?” 26 Jesus answered, “It is he to whom I will give this morsel of bread when I have dipped it.” (John 13)

I see Dale Irwin beat me to it:

I’ve heard much on the symbolism of the elements given separately, but not much on the symbolism communicated by the act of intinction. I’ve attended as a guest two services where the Supper was by intinction. Both times I felt, not like a disciple of Jesus partaking, but more like Judas dipping the sop (the “sop” at the Passover meal was a fruit puree mixture, so dipping bread into fruit juice is closer to “dipping the sop” than what many realize.)

When I visit a church and intinction is practiced, I am placed in a very difficult situation: do I violate my conscience by “dipping the sop,” or do I violate my conscience by abstaining from the Supper when I otherwise ought to partake?