Google has announced to turn-off the track change feature of Google Reader. This feature was introduced in January this year, and enables users to track changes in any web page even when that page does not provide any RSS feed for the changes. Hence, this feature helps users to monitor any web page for the changes. According to Google, this feature is not very popular among users.
Google says regarding this, "As of September 30th, we’ll be turning off track changes in Reader. Your previous updates will not go away, but you will stop receiving new updates from any custom feeds you have set up.". Google has not mentioned any reason behind this shut down.