a little wager.....backfiring

A couple of buddies and I have a little wager going between us on a discussion that I initiated. I won't state which side I am on, as to not be biased.

A car is trying to start, but keeps backfiring thru the exhaust(technically called and afterfire). Is the timing too retarded or advanced? Is it a fuel issue?? Also, a backfire thru the carb is caused by what??

This is just a friendly wager(couple of pints between friends). Just thought this might be a fun discussion here on the board.8)