No address is required if you fall in the category of "persons who are in transit to a location outside the United States" (see 19 CFR 122.49a(b)(3)(xii)).

If BA won't allow to check you in, then BA is not compliant with US law; contact them to get this fixed to comply with the law.

P.S. The "in-transit" notation is procedure for applying for the ESTA: http://www.cbp.gov/xp/cgov/travel/id...wp/faq_vwp.xml