“…During the promotional period December 15, 2011 through September 17, 2012 companies can take advantage of as many external user licenses as they need. If your company exceeds its current license allocation contact support and salesforce.com will happily grant you additional licenses. After this promotional period your company may keep these licenses at no cost. For example, if a company needs 1,200 external user licenses during the promotional period it will keep 1,200 external licenses for free after the promotion expires. After September 17, 2012 companies may purchase incremental licenses above what they received during the promotional period…”
read more at Chatter Customer Invitations FAQ – Salesforce.com.
SalesForce Chatter is a great way to collaborate with the customers, but I think unless the pricing is very low and in large volume, it will be counter-productive and hurt adoption if SalesForce users/Group Admin have to consider license ramifications when making groups available to customers and external users.
