This seems to be all the rage (and I like it). Feltron did it first. Nike+ in a different way not too long after. Wii Fit last year. Foursquare recently.
A few thoughts:
#1. I don't think the stats at the top are that interesting unless you can see stats-over-time (we're guilty of this with foursquare too). I want to see progress (like Wii Fit shows me). How is my usage making me a better person (is that too much of a strech?) or more interesting? With foursquare, we're hoping to get to the point where we can (a) encourage people to do new things and (b) show people stats on the new places they've gone/ new people they've met / new things they've done ("progress over time") and I'm wondering if Tumblr can expose something like this via categories/tags/reblogs, etc. Are you talking/blogging about new/different things then you were 3/6/12 months ago? Are you discovering more stuff (as opposed to re-blogging) than you were before. Are these stats even interesting to people besides nerds like me? :) Hmm..
#2. Wish I knew the secret sauce that makes "Tumblarity" -
know the algorithm? Is it posts? Or influence/ audience? Or a combination? (I'm hoping it's more influence/ audience). I really like the "up/down 10" since yesterday thing. I've long wanted to do stock market popularity indexes based on dodgeball (now foursquare) activity (we expose a little of this with the "Top Friends" in foursquare stats and the old "Best Friends Index" I used to have on teendrama)
#3. "Followers" and "Likes" strike me as good forms of social currency (I'm surprised Twitter doesn't also do "Likes")... we could use more of this w/ foursquare. I wonder if Tumblr is going to do anything besides just collect and rank based on them. We've been talking foursquare points translate into [insert highly covetable item] here... I wonder if Tumblr can find a way make this work too.
#4. I'm not the first to say this (Peter Feld?) but I think the stats may increase the signal-to-noise ratio on Tumblr (in the same way that foursquare points have increased the number of not-so-interesting checkins on foursquare... e.g. haircuts, coffee shops, subway stations). I think we [foursquare] can get away with it because more checkins = more chances to meet up (, right?) tho I wonder if this will cause Tumblr to feel "less curated" (in the same way Twitter is starting to feel these days) because people are trying to run up their numbers / Tumblarity.
Still, looks very hot tho and looking forward to see how this evolves. Nice job David + crew.