Forrester is telling the world that Facebook fans are more likely to recommend, consider, and purchase from you than non-fans.

Their research cites these examples:
BlackBerry Facebook fans are 400% more likely to recommend the brand to friends and family.
Coca Cola Facebook fans are almost 50% more likely to consider a brand purchase.
Best Buy Facebook fans are almost 200% as likely to have purchased from the brand in the last 12 months.

Fans = Good. Bottom line.