The story is even stranger, the man, Tareq Salahi is a prominent Palestinian lobbyist, and board member of American Task Force on Palestine (although they have edited him out of their website since this party crashing story broke). The ATFP is an organization that promotes Palestinian issues and is active in the discussion of the Israeli/Palestinian conflict.
The group was formerly called American Committee on Jerusalem and was headed by Rashid Khalidi. Obama and Khalidi are friends, having eaten at each others’ homes often.
This information comes from an article “White House party crasher ties to radicalism and Obama knows him” in the Hartford Conservative Examiner.