PostRank, the impressive social media tracking service, has just been purchased by Google. Many bloggers, including me, have been using PostRank as a tool to measure how “engaged” readers are with our posts. I publish a monthly list of my most popular posts based on their analysis, and have a widget on my sidebar that is constantly updated.

Google does not have a good track record of keeping their new acquisitions going and, since they’ve announced that PostRank is not accepting any new registrations, this could be a sign that the same might be true here.

You can read more about the acquisition at TechCrunch and ReadWriteWeb.