I wrote a fan fiction dealing with lots of flashbacks just to see how it would go. A lot of people liked it, but honestly I found it very difficult to keep track of what felt like two different stories. Plus it interrupted the flow of the story. So I'm not going to say that it can't be or shouldn't be done. But it is definitely a challenge to do it correctly.
You need some sort of strong construct that allows for, or even forces, the flashback, or a really really strong thread that carries the story line through time. Kinzville's original post reminds me a lot Breaker Morant, about the trial of a group of British officers during the Boer Wars. The main time frame is the trial, and the flashbacks - induced by the trial testimony - are all of the events in the past that lead to the trial. Great yarn. Another example: last year's movie The Imitation Game was an interrogation-induced flashback-a-thon.
