I definitely believe the flashbacks are real depending on what your definition of a flash back is and how much LSD you have done in a certain amount of time.
I used to have a pretty big supply back in the day and was taking about 3 hits a day for a week straight, then i dropped it down to tripping about twice a week for a few months. When I stopped doing LSD all together every now and then I would get a quick blur come and go and my eyes were more sensitive to certain patterns. Like there was a carpet with this funky pattern on it in the local wendy's and it used to seem like it was moving a bit, like one of those optical illusions that make you see movement when it really isn't there. That kind of stuff only happened when I stopped doing LSD. Again, it was nothing major, but just slight optical illusions type stuff that would happen every now and then. After a few months of not doing LSD it stopped happening.
I consider that a flash back. If you consider a flash back seeing purple monkeys popping out of nowhere and then disappearing, then no I haven't had a flash back :)
