The only problem I have with Reddit from a valuation perspective is that it doesn't really offer much 'secret sauce.' The tech itself is not great, and I don't really know of anyone who likes the redesign. Point being, the value is all in the users and content. Users are fickle, and as we saw from Digg (and lesser extent, StumbleUpon), can flee en masse at any moment. That's a tough pill for me to swallow as a potential investor.