Looks like facebook just upped their ante in it's game to squash twitter.
It'd be really interesting to see numbers, but I'd bet usage on facebook has gone up massively since their redesign and new emphasis on the 'stream'.
It's funny, because when the redesign went live, about 90% of my friends where bitching about how they 'hated' the new design. Now they're the most active people on my list.