There is no problem with getting miles from different FF accounts from the same restaurant.
I am registered in AA/UAL/NWA/Delta/HP and one particular month went to the same restaurant/bar 5 times ( its the local hangout for friends and I) got miles on 5 airlines ( by using different cards)
What I am not sure about is getting miles for the same airline more than once a month even if you use multiple cards.
Mike
[This message has been edited by MIKESILV (edited 02-04-2002).]