Isn't constantly asking for a source just a nice way of saying you don't believe the guy? Not everyone reads history or reference books and takes copious notes like we did in college. A lot of reading is done for pleasure and a lot of knowledge can be learned from this reading. I'd bet that most of us don't run and jot something down so we will have it handy when some guy says we are full of it. I think it is kind of rude to constantly say "Source?".