Nothing changed, google constantly seeks out better ways to strengthen its tracking, this could be part of it, may also be temp. no official word from google out yet about this...may be wait a few days, questions about this is popping out everywhere on the web now. But be content that its not a virus of some kind as was previously being assumed... The thing is that in last 3 or 4 days, google has added and sorted out few glitches on youtube section and also trying to link it with g+. The most probable answer is the new chrome 28v rolled out 3 days ago