I reckon that a phone call weeds out 99% of wankers and would-be scammers (as either buyer or seller).
I also reckon that lots of people are far too paranoid about "security". Yeah, I know that plenty of bikes get stolen, but there's a difference between "protecting your stuff" and "being a difficult, annoying fudgewit who is undermining his own chances of making a sale" (not specifically talking about this seller, but you can see that his attitude has deterred a few potential buyers).
Nothing is more off-putting than a seller who has been watching too many old spy movies, and thinks that telling you nothing makes him a hero.