Apparently, some even noticed this back on 17th of this month. B T Collins has an interesting explanation of these Google Update:

• "It seems random and it should be.
• Google cannot tell you when they are going to do an update.
• If they did everybody would have links, real or artificial, ready and waiting.
• As soon as Google indexed the links people would then let the links drop until the next time Google told everybody they were going to do another update".

Discussion continues at Digital Point Forum.

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