As expected, Salesforce.com announced a freemium version of its enterprise collaboration product Chatter today. Chatter Free will use an invitation model. Any Chatter user will be able invite any colleague to Chatter, even if that colleague isn't already a Chatter user. We selected Chatter as ReadWriteWeb's new enterprise product of the year. Update: Marc Benioff announced during his keynote that in addition to Chatter Free, which is free for all colleagues of Salesforce.com users, Chatter.com will launch in February, 2011. Chatter.com will be free for anyone.

It's not clear yet what the limitations of the free version are, but according to Salesforce.com's announcement Chatter free features:

  • Profiles
  • Status Updates
  • Real-Time Feeds
  • File Sharing
  • Groups
  • Filters
  • Invitations
  • Chatter Mobile
  • Chatter Desktop

"Salesforce is basically saying that its 2,000 sales reps can't get the job done and that they need to copy Yammer's model," Yammer CEO David Sacks told us. "This is like Goliath dropping his sword and armor and chasing after David with a sling-shot."

However, Sacks cautions: "Other people have tried to copy our model, but aren't showing similar growth. Salesforce may find that it's more difficult than it looks."

Disclosure: Salesforce.com paid for a plane ticket and hotel room for Klint Finley to attend the Dreamforce conference in San Francisco.