A former U.S. Department of Justice lawyer and antitrust expert says Facebook’s purchase of photo-sharing site Instagram will take between four months and one year to clear regulatory hurdles. In the meantime, the deal is effectively on hold. […] If Facebook can have Instagram, it will be a leading player in photo sharing both online and on mobile. (See Om’s explanation here). The FTC is concerned Facebook could become a dominant advertiser on these platforms — and hurt competition.