Everyone talking here about minutes between blocks and all but I have one curiosity.  If you have a transaction with one confirmation.  How easy is it really for the sender to scam you from the second or third block on?  Because this seems like something only someone with a large enough incentive could do, so I wonder if it is worth the effort for scamming someone out of $1,000?  Does this happen often at all or do you have to be very unlucky to fall for it?  Except unconfirmed transactions which of course are easy to replace.

I get the paranoia, I am an extremely paranoid one myself.  But I typically consider my transaction confirmed once there are two confirmations, unless the sums exceed thousands.  I sometimes consider a large transaction as 'final' after it gets confirmed twice only.  Pmalek mentioned a few replies above that generally, 6 confirmations are accepted as 'final'.  With 4 or more confirmations, is it not just pretty much impossible to scam someone unless we are talking about a significant, BIG incentive and one unlucky person to be in the wrong place at the wrong time?

-
Regards,
PrivacyG