Its true at times SO goes into "crazy mode" and closes useful questions and downvotes good answer, its a known condition as "human condition" , but overall SO is very useful for getting answer to questions and definitely is good promotion of pharo.��
Please note also that a question can be turned into wiki which also useful. I closely follow SO pharo tag and I track this tag and smalltalk tag and I am notified for any new questions using these tags. Surprising the majority of smalltalk questions are pharo questions which is very nice indeed.��
I dont know how much work would be if the pharo website would offer an online forum. If pharo grows in popularity I am not a fan of managing my messages via a mailing list.��
Blender which has already an extremely popular forum here (with at least 1 million posts)��
http://blenderartists.org/forum/ , has also chose to move to Stack exchance and has its own domain there for questions about blender. Emacs also recently ported to stack exchange.��
So Stack Exchange is here to stay and will all its disadvantages still a very good deal for pharo. Stack exchange, with Stackoverflow a part of it, ��is actually huge and probably the most popular ? forum ? out there and it keeps growing.��