I've seen several mentions of portals sharing users here in the AS forum, but no one really mentions what modules they are using and why..  I'm curious to know these things...

1. Do you have user sharing between portals on the same DNN install with Active Social & Active forums?
2. What modules do you use to accomplish this and why did you decide on that module? (DNN Masters, Data Springs, etc)
   
3. Are there any drawbacks to this config?
   
4. Are there and advantages?
5. Any 'gotchas'?

I have several other sites that I'd like to develop.  There are definitely going to be 'crossover' users between the sites.  I tried it once before and the most common question I got was "why do I have to register again?"  Why can't I use the same account?

I can tell you that we have seen several implementations covering all the possible modules. The one from DNN Masters definitely will cause some problems because it doesn't recreate the profile data properly. I will come back to this topic in a few days with more details and recommendations.