I do not feel qualified to comment on how to approach the categorization of ME. I am sure more learned people than I will comment.
However, growth of the PP membership got me interested. So I did some sums.notice we have 1251 members now, more than 250 in one year!
On 21st August 2009 there were 406 members..... an additional 845 in three years.
On 21st August 2011 there were 899 members..... an additional 352 in the last 12 months (average of just under one a day!)
The rate of growth has indeed been amazing in the last three years and clearly seems to be accelerating.
Best, Ant