The One Cup Position:
1) Jesus only used a single cup in spite of the Passover tradition. They put away their multiple cups and then passed around a single cup. When Jesus said to divide it among yourselves, that had to mean that they each took a drink of the one cup, and that is how it was "divided up" among themselves. In addition, Mark mentions that they all drank from "it" (singular), so they used only one cup.
2) This was the "Lord's Supper", not the Passover. Luke 22:20 says "in the same way, He took the cup AFTER SUPPER saying..." So it was AFTER the Passover that they partook of the Lord's Supper. Therefore, Passover customs are insignificant, because it was after the passover.
3) Since Jesus only used a single cup, then we must also use a single cup. Jesus said to "do this" in rememberance of me. The "this" was said in reference to the single cup. So we must use a single cup to be obedient.
4) The cup is significant because to use more than a single cup would destroy the meaning of the cup. The Cup represents the covenant (Jesus said this cup is the new covenant in my blood in Luke 22), the fruit of the vine represents the blood (Jesus said this is my blood of the covenant in Matthew 26), and the bread represents the body of Christ (Jesus said this is my body in Mark 14).
5) One cup should be used, because that is the safe thing to do. We would not want to gamble and be careless, but do what we know is safe.
The number of cups is of no importance position:
1) There is ample evidence that each had his own cup due to the Rabbinic Passover instructions of the day. Jesus clearly said "I have earnestly desired to eat this Passover with you before I suffer". The context makes it clear that this was the Passover. During the Passover, each participant was to have his own cup. If he couldn't afford one, it was directed that he was either to pawn his clock or hire himself out to get his own cup.
2) Since it was taken "while they were eating" (Mark 14:22), it was during the Passover, and each would have had his own cup.
(Note: the word "supper" is actually a verb, but it has been translated as a noun in some translations. So a better rendering would be -- "similarly, after they ate, he was saying..." -- So it wasn't after "supper", but after they ate of the unleavened bread that they took of the fruit of the vine. Notice the placement of the phrase, "after they ate", between the taking of the bread and the taking of the fruit of the vine. The accounts in Matthew and Mark make it clear that this was during the passover.)
Jesus took the cup and told the disciples to divide it among themselves JUST BEFORE he gave significance to the bread and wine (Luke's account). This is in total harmony with the fact that each was to have his own cup. The Mark passage could also be translated that they all drank "OF" it, meaning the contents. This fits in with the fact that the fruit of the vine was divided up among themselves BEFORE they partook of the bread and partook of the fruit of the vine.
3) If Jesus had taken a cup and passed it around, and each emptied some of the contents into their own cups, -- and Jesus then held his own cup and said "this cup (singular) is my blood of the new Covenant", -- it would still be an accurate account even though each person had their own cup.
4) When Jesus commanded to "do this in rememberance of me". He wasn't making reference to a cup, but to the fact that they were to observe it in "REMEMBERANCE" of him. "Do this" proves nothing about one cup. Even if they had one or many cups, he could still say "do this in rememberance of me", and it would prove nothing about the number of cups.
5) We don't simply practice something during the Lord's Supper simply because that is what the first disciples did, otherwise, we would also recline, take it at evening, and do it in an upper room on Thursday. If they had a single cup, it doesn't necessarily mean we should. Just because they had multiple cups doesn't mean we should have multiples either.
6) What we do in the Lord's Supper is very much linked the the meaning (or symbolism, sign) behind it. Reclining, Upper Rooms, and Evening have no memorial meaning behind it, therefore they are insignificant.
7) Both the Gospel Accounts and Paul's account make it clear that the "cup" refers to the contents of the cup. "For as often as you eat this bread and drink the cup, you proclaim the Lord's death until he comes". When we ask for coffee and say "I would like a cup", we don't mean we are drinking a cup, but the contents of it. We do not proclaim the Lord's covenant, but his death when we partake (I Cor 11). To talk about the blood of Christ and his death is talking about the same thing, the life is in the blood, which is what Jesus offered to God on our behalf. We remember the shedding of his life when we partake of the fruit of the vine. The Cup clearly refers to the contents.
8) Jesus made no distinction between the cup and the contents of the cup, contrary to the one-cup position that the cup represents one thing while the contents represent another.
9) If the cup (which clearly means the contents of the cup) represents the covenant, then nothing represents the blood! This is the obvious conclusion if each account of the Lord's Supper is read carefully. The ONLY way to make the assertion that there are three rather than two elements during the Lord's Supper is to mesh the accounts together into one as if for some reason Matthew and Mark forgot to mention the fact that the cup represents the new covenant. By that same token, it would also mean Luke forgot to mention that the fruit of the vine represents the blood! None of the accounts of the Lord's Supper mention three elements, all mention only two. So, if the cup represents the covenant, then there is no blood represented, and the blood is what established the covenant in the first place!
10) There is nothing wrong with playing it "safe". Just the phrase "playing it safe" suggests acceptance of the fact that one may be mistaken about his interpretation. The Pharisees play it "safe" as well. However, it became a problem when they forced it on others and gauged other's spirituality on the basis of the own interpretations (or as Jesus called them "traditions"). As a matter in fact, Jesus said "In vain to they worship me, teaching as doctrine the commandements of men"
11) All in all, looking at it practically, it would be impossible for large congregations (such as the 3,000 on pentecost, or even the 1,000 in a modern congregation) to meet and worship on the Lord's Day. We would have to partake of a "Jug" or a "Barrell", which would not be practical.