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What: Shares of AVG Technologies (NYSE: AVG) plunged today by as much as 12% after the CEO resigned.

So what: The news comes just weeks after AVG jumped 14% on better-than-expected earnings and guidance. J.R. Smith said he is stepping down but will stay on as CEO until a successor is found. COO John Giamatteo will handle daily operations until then.

Now what: Smith said he felt it was the right time to hand over the reins to new leadership. He had led AVG for the past six years. The outgoing executive will become a member of AVG's Supervisory Board, and AVG has tapped SPMB to search for a new CEO. Investors are caught off guard from the move, and that surprise is manifesting itself with today's sell-off.

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