What numbers are those? I didn't think anything was public, and probably never will be now that the company is privately owned.
I just know anecdotally, I've been a long-time Twitter user (user id #1661), and the current mood on my feed reminds me of the Digg-Reddit exodus. It's not about the raw numbers (yet), it's about who's leaving and who will follow them.
any numbers? from the numbers i've seen, twitter is doing quite well.