Excuse me gentlemen!
Since this thread has been hijacked to FICO scores, I'll answer the original question. I currently have 2 active personal Citibank AA Platinum Mastercards, a business Citibank Visa card and have just received a Citibank AA Amex card. I have collected 60k bonus miles on the 3 Mastercard and Visa within the last year. I am awaiting 15k on the Amex card.
So to answer your question, Yes you can have multiple active Cards from Citibank. If your not buying a home or refinancing in the near future and your FICO score is not an immediate concern. You can just apply after all, all they can say is no.