If they found a yahoo employee credentials in the linkedin hack (or vice-versa) then they don't need a million accounts, just those credentials. "Hackers who u

If they found a yahoo employee credentials in the linkedin hack (or vice-versa) then they don't need a million accounts, just those credentials. "Hackers who used an employee’s password, re-used from the LinkedIn breach, to access Dropbox’s corporate network and steal the user credentials" - from a unnamed source quoted in a techcrunch article. So maybe they also managed to traverse from linkedin to Yahoo or Yahoo to linkedin through similar password re-use.