More importantly is the death of two key resources: mybloglog & technorati which enabled bloggers to publicly keep track of trackbacks. I used it all the time and ended up with sizeable audiences!
Technorati had terrible management. I was very frustrated trying to deal with them. In 2006 myself and friends were trying to build a startup that would rely heavily on Technorati's "Authority" ranking. Technorati supposedly had an API, but to use it we were supposed to write to the company and negotiate a price. I wrote to them 20 times. No one ever wrote back. Out of frustration, I tracked down some of the top people online, found other email addresses for them, and wrote to them. No one ever wrote me back. We were desperate to give them money, but they did not want our money.
I don't know ... I feel like those aggregation sites ended up killing the golden goose. People stopped visiting individual sites (and adding them to their browser favorites) because they could just visit the aggregator, and eventually they became the primary destination ... so maintaining your own blog was merely a way to get onto the aggregator.