"The Google/DoubleClick merger would harm consumer welfare by creating a structure that almost certainly will be less respectful of user privacy," the BEUC said Thursday in a letter to the European Commission this week.
Last month, the European Commission, the European Union's competition watchdog, opened an in-depth probe into the proposed takeover, saying it raises competition concerns in online advertising.
Google, which uses consumer queries to choose advertisements that appear on Web surfers' screens, wants to buy DoubleClick to increase its clout in tailoring advertisements to consumer activities.
"Post-merger, Google will have the ability and incentive to engage in significantly more intrusive user tracking and profiling than exists today," BEUC said.
The lobby group also said that the merger would place the online advertising market in jeopardy because the combined company will dominate both major "pipelines" for online advertising--for search ads and nonsearch ads.
"There are many ways in which Google, post-merger, could push up prices for advertisers," BEUC said.
The higher prices for advertisements would likely be passed on to consumers, the lobby group said.
The Commission has until April 2, to make a final decision on whether the proposed transaction would significantly impede effective competition.
©2007 CNET Networks, Inc. All rights reserved. CNET , CNET.com , and the CNET logo are registered trademarks of CNET Networks, Inc. Used by permission.


