Agreed that buying anything used involves risk. The idea is to minumize that risk by knowing what to look for and asking the right questions to the current owner.
The Busa makes vehicle number 24 for me and all but one were used. Take a wild guess on which one I had the most problems with....yes, the brand new Ford truck. The first six months of ownership and the stealership (I like that name) had it more than I did. Wound up selling it before it was one year old. Not to say that they are all bad just like not all used vehicles are bad but you have to be careful.
Once I narrowed my sights on the Busa (excellent choice btw) I spent close to 5 months looking into bikes before I found my baby.
I got so fed up with scams (100Cycles.com) I sat out briefly before realizing I had to change my expectations. The old rules still apply, if it seems too good to be true, it usually is. Much better luck was had on cycletrader.com but even then it took a couple of months of constant looking and emailing and phone calls and even at that I had several bikes that were good deals slip through my hands because I simply could not get there in time.
I was very fortunate that the gentleman I purchased my bike from was one of integrity, he held the bike for me since we agreed on a price even when someone offered him more money, or I would have lost this one too. Bottom line is that there are good used bikes for sale, you just have to be patient and be ready to strike when the time comes.
New is nice but it comes with a price....(I'm a poet and did't know it)