[Doctorwhonerd]

Is it due to the cracks.

[sandydune]

it is thought so but something I often wonder about, is that in the Beast Below there was that machine where she could press a button to forget, what else was she shown on the screen? did she forget other things too?

[Si_Crewe]

I asked the same thing a few months ago.

Pretty much all the responses were something along the lines of "Well, of course it was the cracks in time that made it happen", usually followed by "Well, either that or the rebooted universe. Or something. Probably".

Given how often all the confusion about why Amy can't remember Cybermen stomping around London, Daleks or the planet getting towed around the galaxy by a telephone box was mentioned, you'd think somebody would have written a line into the script where the Doctor resolves the issue properly... IF it's actually resolved, of course.

TBH, I wonder if the current crew of script-writers have been told to adopt a policy of writing open-ended or ambiguous storylines so that, in future, new plots can hook into unresolved facets of old stories.
Or, to put it another way, I think they're making it up as they go along now.

[sigsig]

Yeah they're definitely making it up as they're going along. Matt Smith accidently wore his jacket during filming for Flesh and Stone, so they had to create the whole 'personal timeline being erased' story to fit in the error

Amy forgetting the Daleks is, as far as we know, the work of the cracks. Just as Amy's family disappearing is, as far as we know, the work of the cracks. It's only a dangling plot detail if you think it is.

Which is not to say it can't be picked up as a part of the overall mystery, or that it's been part of it all this time. But it's resolved, and to say that it was deliberately left ambiguous is pushing it in my opinion.