Interesting about Twitter going from 500 to 1,900 on Alexa. It's compete ranking and now its most current alexa ranking match up, as compete ranks it 2K.
Though were sure to see it's ranking go back up to 500 and beyond. It's the next huge thing, just like MySpace and Facebook!
http://siteanalytics.compete.com/scribd.com+weebly.com+reddi...
It tells a different story but the outcome is still the same. For Scribd to have higher traffic than Reddit is pretty impressive.