Email marketing can work great in tandem with Facebook.
Many, like Laura O'Shaughnessy of SocialCode, argue to line up email and Facebook programs. Both are low-cost, broad reaching and give you the ability to track ROI.
However, I believe that email is the more direct and more valuable customer list because:
1) Email can be segmented in a way Facebook cannot: pick your objectives, pick your messages, pick your groups, execute.
..But email can also certainly drive social engagement ... if social engagement is your KPI (rather than a financial transaction, for example).
2) Email can directly link the online and offline worlds. Flash coupons, price checking and loyalty programs affect my bottom line long term more than sharing photos and voting for new product names.