"You trade one kind of risk for another, " says Dr. Silberstein, who has served as an investigator on several companies' clinical trials.

WSJ: Fresh Target in Hunt for a Migraine Cure

The thieves "knew exactly what they wanted because the only file taken was the one dealing with the Israeli campaign, " Silberstein said.

CNN: Thieves break into office of Israeli candidate's pollster

But Tal Silberstein, a campaign official for Labor Party leader Ehud Barak, said someone in Greenberg's office had told him the Israeli campaign was the "main focus" of the robbery.

CNN: Thieves break into office of Israeli candidate's pollster