|Lion of St. Mark, Piazza San Marco, Venice|
There are three stories included in this long passage (Mark 2:13-28), and they all follow on one connected theme. Jesus, through his actions, was defining the rules of behavior for his disciples in distinction from the social and religious norms of their society. It's important to note that the disciples are a constant presence of some importance in each story. In 2:16 the Pharisees ask them why Jesus ate with sinners. In 2:18ff their own behavior (failure to fast) is subject to question, and again in 2:23ff the behavior of the disciples (picking wheat on the Sabbath) is criticized. What we have here, in a sense, is a charter for the very earliest church. The Jesus Circle, according to Mark, maintained close social contact with social marginals and even includes them in its numbers. It defies conventional expectations concerning pious behavior (2:18-22). And, it doesn't assign ultimate significance to keeping the Jewish Law (2:23-28). The author makes no attempt to link these events chronologically. They are, rather, linked by the common theme mentioned above.
It's not clear at all that any of these events actually happened as such. They represent, I think, remembered values, sayings, and stories about the sorts of things Jesus did. Most of the details in the stories are generic rather than specific, excepting the name of Levi, the tax collector, and the fact that Jesus ate in his house (2:14-15). My own feeling is that in these verses we're located as much or more in the author's own time than in Jesus' time. He's defining, if I'm correct, the nature of Christian community for the church itself. He's describing and defining the church's identity, both to explain why the church is different from other religious entities and how church members should behave. Mark 2:21-22 (new patches and new wine) highlight the theme that the life of the new community is different from the social and religious norms of society. The church contains new wine (Jesus? the Holy Spirit?) and it requires a new wineskin. What we have here, in sum, is quite possibly a second generation Christian saying, " This is who we are. This is how we became who we are."
2012 comment: However, it is important to understand that the earliest church built its identity on its historical experience with the actual person of Jesus of Nazareth. Whether or not the stories reflect particular events or the church's memory of "the way" Jesus did things more generically, they still originate in the church's memories of Jesus.