My guess is that there was some ugly situation in Korea and the real Don Draper is killed - and he grabs his dog tags. And then Dick Whitman is listed as dead or MIA.

so, Mad Men is stealing plots from The Simpsons?

That part I figured on. But is there something he's covering up, or is his family life just that trifling. It's kind of funny...he was his own first ad account. Sorta.

That is what he's covering up - he's not who he says he is. Why should it be more than that?

No special reason, but I thought there might be because of his wartime traumas and whatnot. Also, while I have joked about Changing My Name And Moving Away, Don really did.

I think there's something in Dick Whitman's past before or during the war that was so traumatic he had to change identities to escape from it. I'm guessing he killed someone outside of the war - maybe uncle mac?

I'm guessing that things weren't happy with the fosterparents and he just seized the opportunity.

I thought that the "mom" had died first -- but after he had left home.

The Inflation Calculator

What cost $5000 in 1960 would cost $33405.09 in 2006.

Yeah, I agree with erika that there may be more to it. His level of desperation to keep anyone from knowing about the existence of his brother seems to indicate that there's serious damage that could be done to him now.

eta: Oh, Tom, thanks. I was wondering about that.

So, you think he fragged Draper?

I mean, wouldn't Draper have real family somewhere in the USofA - possibly thinking that he is dead/MIA?

Of course, it would make sense that Draper is the real orphen and he was raised in his real family who were just dirt poor and he is that ashamed of them.