Call it what you will but I had no idea that TWA miles transferred to AA and I fly AA almost exclusively so lost only about 40K combined with my wife. My address had changed during the transition and so TWA most likely could not match my AA account.

My wife who travels infrequently has lost most of her miles but they only range from 5K - 20K on virtually all airlines / hotels. The only other ones I've lost are Hilton when I neglected to stay with them for a long time but that was only about 40K Hilton points. Although I deserved to lose those Hilton points, it does make me not want to stay with Hilton, perhaps because I have to start from zero and rather just build up my other hotel points.

Personally, I do find it hard to keep track of those programs that I don't stay / fly often and where I don't have a credit card.