Some of us are ok, in fact probably the very great majority, it's just that there are enough mongrels to spoil it.
I recently bought a bike from Wolverhampton (over 12,000 miles away) on the basis of some email photos, a very happy deal. The vendor was sort of known to some at the far end of the network, however, so I never even considered the scope for fraud.
It's not sufficient reason to not trade by correspondence, so long as you are careful, do truly apply "due dilligence" and are not merely smitten and love-struck.
cheers,
JFerg