There is a very easy way to detect the validity of a scam (or at least
right now).  I have had genuine offers from Dave Caldwell and Robin
Pratt, that I knew were genuine, on items that I wanted to buy: a recut
roll or reprint and I knew that they would have more so I went through
with them.  On all of the instances that were genuine, eBay identified
my real name and offered a buy-it-now link that went directly to eBay.
I don't know when the scammers will get over these two obstacles.

I would offer the following advice:  If you get a buy-it-now offer on
a Second Chance item that you want, you can try verifying it with the
seller of the original listing.  Use the eBay item number and ask a
question, if they don't have any current listings, contact the eBay
member.  For something expensive that you're really interested in,
ask for a demonstration of it.

Eli Shahar