Points are accumulated, but (my reasoning) for ppl saying they are 'losing' points is because the media still refers to it as losing demerit points. This implies you had points to begin with, which you dont.
From memory, in the double demerit weekend ads, the voice over dude says '...lose 6 points...'.
another example: http://www.news.com.au/story/0,23599,22502...from=public_rss