KEY POINTS:
The European Commission will open a four-month, in-depth review of Google's plans to buy rival DoubleClick for US$3.1 billion ($4 billion).
Google, which stores data on the internet-surfing habits of consumers, wants to buy DoubleClick to increase its clout in tailoring advertisements to consumer activities.
Critics have raised questions about what effect the deal might have on privacy, but the commission has said privacy by itself is not part of a competition review.
