October 13, 2010
I have had this question quite a bit lately and have written a synapses about my experiences and understanding with new changes, etc. I also use a page for reference at times (http://www.allfacebook.com/facebook-groups-pages-2010-02) which may have some outdated information on it now, but most is pretty relevant.
Fan Pages have two types of interaction for Facebook members: Admin or users. The reason its admin is because the fan page is supposed to be run by the core person/group that is promoting the name brand, etc., and controls the information being sent out to the fan base.
The Groups allow for multiple levels of users, officers, etc., to offer some flexibility, hierarchical recognition within an organization, awards, etc..
Fan pages are more about promoting the brand/name/blog/band/person while the groups are designed more for user interaction from many people.
Fan Pages offer statistical information about the users, posts, interactions, advertising campaigns, etc., while the group does not.
Fan Pages do not allow the admins to message all the members, Groups do allow for this.
Truly to run a campaign there is a mix of group and fan page interaction in addition to other social media markets. It sounds like a LOT but the biggies such as Pepsi, Old Spice and more have directed more than 50% of their marketing campaign funds towards this mechanism to reach 400 million people for less than it costs to run one television ad in 200 markets one time in one day.
Hope this helps you out some!