There has been a thoughtful discussion at Amusicology about the relatively small number of musicology blogs (a number substantially reduced Ithinks by the recent end of Dial "M" for Musicology) .
The reasons are, of course, manifold and complex, but I believe that a major reason has been an attitude towards publication which has come to dominate the practice of academic musicology. This attitude focuses on publication directed towards fellow and sister academics rather than to a more general public, and is carried out through the publication forms most likely to be credited in hiring, tenure, and promotion decisions (and — coincidentally or not — the ones you can access only if you have the independent wealth to afford a subscription or have access to a good University library or JSTOR). While there are, indeed, advantages to these publications, the quality filters of peer review among them, and the necessity of some filters given the terrific strain placed on the profession by the limited number of available academic positions must also be recognized, this leads to a general avoidance if not disregard in the profession of forms of publication intended for wider audiences, blogs among them.
Musicologists do appear in marginal news stories from time to time — when discovering or authenticating a long-lost manuscript or as forensic witnesses in plagiarism cases — but the general invisibility of the profession, particularly in making a wider public aware of some of the more extraordinary attributes and excitements of music has got to be a long-term form of shooting oneself in the foot. Now we can have some substantial disagreements about the directions which musicology has taken (i.e. the move to a more contextual/historical/sociological musicology and away from the production of editions, biographies and reconstruction of performance practice*), but there ought to be some consensus that a more public musicology would be advantageous in securing and building on the current status and numbers of tenure lines in comparison with the current, closed-circuit approach. The natural sciences have done a very good job with making their work public and even popular and perhaps that should be the model. (If there's a Science Friday on public radio, why not a Musicology Monday?)
Two other small observations: The first is that blogs can fill one particular niche in musicological publication that the major journals appear to have largely abandoned: that of the small item, detailing a minor but not unimportant finding. Some years ago, I had a great conversation in Budapest with the late theorist John Clough, in which we bemoaned the fact that academic writing in music had become largely limited to the form of a substantial essay, while many results, insights, and discoveries were smaller than that particular breadbasket. Moreover, with journal publication schedules on perpetual delay, there was little sense of timeliness in publication, and timeliness is certainly an attribute of the excitement of a discovery. Blogs, lists, and other forms of internet publication can certainly fill this void.
The second small observation is that with the natural attenuating affect of the tenure process, forms of publication which focus almost exclusively on an audience in the academy are unnecessarily distancing themselves from some of their most astute, best informed, and, potentially, most usefully critical readers. The function of musicology in a University is not only to produce more musicologists but to produce more professional musicologists but to produce a more musicologically-informed body of musicians and audiences. Within this body, the trained-but-amateur musicologist is a noble and undervalued element as well as a natural ally outside of aceme who is disregarded at the peril of the profession, and more essentially, at the peril of the advancement of musicology and music-making in general.
* Need I note that the long-overdue production of an edition of the works of Johanna Beyer has come about by the volunteer work of a consortium of composers and the Frog Peak Press cooperative, not by musicologists and a University press?