Dollhouse's ethical dilemma

Yesterday I watched the first episode of Joss Whedon's Dollhouse on Hulu, a drama in which the heroine Echo's memories are regularly expunged and recreated by a secret organization. The process allows Echo to forget painful experiences in her past. But in forgetting life's most painful lessons, she loses knowledge that could help prevent future tragic occurrences. Then today I read this article from the BBC about how a heart medication could suppress the emotional intensity of memories, allowing people to blunt traumatic effects of the past. The parallel struck me immediately, and it made me wonder: How should we help individuals cope with past trauma? Six years into the Iraq War, we have no shortage of citizens suffering from traumatic experiences: war zone conflicts, the death of loved ones, job loss, and home foreclosure. Some people have been so affected that their everyday quality of life has declined dramatically, and perhaps for individuals, starting over with a clean emotional slate would seem a blessing. Imagine for a moment that it were possible to push a giant reset button on the collective American psyche, that with the aid of a little pill, we could wipe out all our past suffering and look into the future with vision uncolored by experience. Imagine that happened right before the 2008 election.

Tell me, exactly which lessons are best forgotten?