For too many, still, "church" and "synagogue" are merely code words for a weekly ritual in a specialized building. Thus, the argument is sometimes put forth that (A) the earliest christians kept most or all of their Jewish customs, (B) that included synagogue gatherings, and (C) therefore, the early church was every bit as "structured", "ritualized" and "formal" as the Institutional Church's typical Sunday gatherings.
Ta-da. Present system justified! There's just one little problem. Early synagogues may not have been quite like what these IC defenders were assuming they were.
Did early churches look anything like early synagogues? Well, in some respects, to some degree or another, yes. Of course. But what are we asking about - communities or programmed assembly meetings? And in either case, which aspects were similar? How so? And how much diversity was there?
Most importantly, whether we're researching the lives of communities or the liturgies of their holy gatherings, we can't really compare ancient churches to synagogues without backing up all the research and asking the foremost necessary question: What were early synagogues actually like?
That's somewhat of an open question at the moment, but for an excellent primer, you can start with two of Alan Knox's recent blogposts:synagogue leadership. That topic needs much more discussion, but not at this very moment. Anyway, all of Alan's posts are well researched, challenging and informative, so head on over!
Update (4/5/10) - Alan's at it again: Points of comparison between the early synagogue and early church.