Here's a quick overview I found of the Q hypothesis and the people who formulated it.
For some one like me, who's learning and learning some more, the article gives a lot of information about the history of the Q hypothesis.
It also goes into some detail about the hypothesis' lack of acceptance by a good number of scholars.
http://www.theatlantic.com/past/docs/issues/96dec/jesus/jesus.htm
"However, the hypothesis is not without problems, which have led to its rejection by a significant minority of scholars. The primary problem is that although Matthew and Luke often agree with Mark but not with each other on details of the triple tradition, they also often disagree with Mark while agreeing with each other. How can this be, if their authors were working without knowledge of each other's work? For example, Matthew and Luke will sometimes change one of Mark's colorful, if rough-and-ready, Greek words to a more polished Greek synonym -- the same synonym in both. Or both will omit one of Mark's vivid details, such as the fact that "four" men lowered a paralytic through a hole in the roof for Jesus to heal. These "minor agreements" between Matthew and Luke against Mark are numerous but picayune, and most two-document defenders attribute them either to coincidence or to efforts by the scribes who recopied the Gospels to make their language match. However, in half a dozen passages Matthew and Luke have taken a complete story from Mark -- Jesus' baptism, for example, or his temptation by the Devil, or the parable of the mustard seed -- and significantly reworked it or expanded it in almost exactly the same way. Indeed, the favorite "Q" passage of Q scholars -- Jesus' "mission" instructions to his disciples not to carry food or money on their travels -- is not, strictly speaking, from Q at all but from a section of Mark that Matthew and Luke rewrote in parallel ways. These "major agreements" between Matthew and Luke against Mark in triple-tradition material have come to be known as Mark-Q overlaps. They are very difficult to explain without hypothesizing that either Matthew or Luke had access to the other's Gospel -- which would obviate any need for Q in the first place."
"... if you believe that Mack's countercultural theories, Kloppenborg's layer-peeling, Theissen's wandering-radicals sociology, and Robinson's exhaustively labored-over Q-reconstruction project add up to a genuine leap in our understanding of where Christianity came from. Many scholars do not. "It's all faux history," says Luke Timothy Johnson, a New Testament professor at Emory University's Candler School of Theology, and the author of The Real Jesus (1996). "They put the Q community in Galilee because we know so little about Christianity in Galilee." "It's not sociological; it's simply ideological," says Richard Horsley, of the University of Massachusetts at Boston, a former student of Koester's who remains friendly with many Q scholars, including Mack, despite a wide divergence from their beliefs. Horsley's latest book, Galilee: History, Politics, People (1995), examines the area's society and culture during the first century. "My book pulls the rug out from under the Cynic sage," Horsley contends. "There's no such thing as a peasant sage, period, in Palestinian Judaism of that time. The sapiential figure -- that's our modern typology, something we've made up. ...."
Then the article get a bit uncharitable
"Attribute the Q phenomenon, if you will, to American enthusiasm, or to American entrepreneurship, or to the American university system, which tolerates more speculative scholarship than the European academy. But there is another factor at work: an understandable lack of willingness to accept that there are limits to what historical research can provide by way of hard information about Jesus and his earliest followers. The only known first-century texts dealing with first-century Christianity are specifically Christian documents, such as the books of the New Testament, and the works of the Jewish historian Flavius Josephus, who wrote at century's end and mentioned Jesus and Christians only twice. So scholars read those books over and over and try to find something new there, or try to bring another discipline -- literary criticism or sociology or anthropology -- to bear on what they read, or hope that archaeologists will dig up new stones and new texts to explore. Given the scholarly urge to break new ground -- especially in America, where there are so many universities -- it is not surprising that an entire industry has grown from the Q scholars' hypothesis."
And it ends, curiously enough, with an even-handed appeal to hope and faith.
Off to read more.
