Here are some reasons I have found philosophy blogs to be beneficial; here I include New APPS (so my bias is obvious), but my comments here are not limited to New APPS, by any means.
First, while I had heard stories here and there of sexism and exclusion of other underrepresented minorities, they seemed like isolated incidents. One could brush them off as the occasional jerk, and think that we didn't need to worry about them as a profession. Because of philosophy blogs, it has now become abundantly clear that we do need to worry about the treatment and the exclusion of women, people of color, people with disabilities, people who are LGBT, etc. And we have started to see changes in the profession to address these longstanding problems.
Second, philosophy blogs have provided a way to share and discuss issues in the profession that aren't directly related to exclusion, but are important to discuss anyway. My recent post on methods for anonymizing papers is a small, if unexciting example of that.
Third, philosophy blogs have provided a way to disseminate news and information (e.g., statistics).
Last but not least, philosophy blogs aren't just about the profession; they are also about philosophy. They have provided a format for wider dispersal and discussion of philosophical issues. This couldn't have come at a better time; philosophy had been becoming increasingly siloed. I think it's still pretty siloed, but blogging has made connections between philosophers that wouldn't have occurred otherwise and let philosophers know about work that they wouldn't have known about otherwise.
Of course, we can all think of postings on philosophy blogs that we found objectionable/harmful or comments that we found objectionable/harmful. On balance, I still think they have done more good than harm.