15-25TB to provide search for the entire internet archive. This is a pretty small number if you think about it. Your avg undergrad class room would be able match it if they pooled all their devices together. So why do we need Google and Bing ladies and gents?
If we can get a 100 devs in every city in every corner of the planet to donate a hardrive/cpuand some time, distributed open search could well do to Google what Linux did to Microsoft. I think its going to happen. There is lot of duplication of the above work going on in little silos like Wikipedia, Khan academy, Stackoverflow, Zealdocs etc it just has get hooked up