Q Who?

I guess what hasn't been explained here is why one would need to assume 
similarities in the Gospels need to be explained as borrowings from a 
single text (oral or written) rather than collections of multiple ones.  I 
assume parsimony would be the reason, but that would not by itself justify 
viewing Q as a kind of "core" gospel - after all, where did the rest of 
the Synoptics come from, if not from other, multiple sources 
supplementary to (or contradictory to) Q, which again leads one back 
to multiple freely-circulating fragments of the Gospels as we have them.

As long as one is spinning out hypotheses, and since there is (seriously) 
little at issue, why entertain one [Q] rather than many?  That is, why 
does the Q hypothesis have such status?  If the answer is too involved to 
summarize, maybe someone could throw out a few articles or books that 
summarize the most contemporary work on Q etc. 

Greg Jordan