I don't do it -by the time you see someone's flash, you would be very unlikely to be able to change the flightpath enough to avoid him by much, if at all, so it's just an interuption.
But, the thing that anooys most is that the morons who do flash, seem to do so without any reasona s to why, when quizzed. Hmmm...doing things by rote...a long and unsuccessful method of operating in avaition!