Chaplin, it is just another source of information for others to collaborate and educate while discussing topics, just like here. For many it's easier to use that as a platform they already use.
Facebook private groups do have these advantages
- files can be uploaded and get stored in one location (ie AA rebalancing spreadsheets)
- can create polls
- can upload images much easier
- can create events
- can share articles and links much easier
The one thing that the forums have here is that there is a higher level of anonymity, less public knows about it and financial information flows a bit more freely.