If my vague memory is correct, using SO_REUSEADDR can (at least theoretically) cause (undetectable) TCP issues. If a connection on a particular (source address, source port, destination address, destination port) tuple is closed locally and then another connection is opened on the same tuple _before_ the TTL time has passed, the new connection may receive (sans error) data which was intended for the old connection (again, IIRC).
Yea at least given modern ISN generation mechanisms I would think it would. Back when I was looking at it, the typical means of ISN generation may have been more naive?
I'm also hazy on the exact fail case...it may also have had something to do with a FIN message getting lost, though I would think that would also be handled by the sequence number.
