The chief question my wife and I have is: How did I end up in Ashley Madison’s dump pile at all? We have yet to find out, but we have several theories. (Happily, my wife did not for a minute think me unfaithful, just as I would not have doubted her; it’s that kind of marriage.) One possibility is that identity thieves put me in the database. It’s well known, of course, that many of the female members’ profiles on Ashley Madison were fabricated, because the site’s users were disproportionately male. But it is less widely reported that some of the email addresses attached to those accounts may well be the email addresses of real people; addresses can be bought in bulk for around 20 cents each from marketing companies. It is not even necessary for the appropriated addresses to have a woman’s name in them—a man’s name will do just as well—because the addresses attached to the fake profile can’t be seen by anyone but the account holder. Some men (and their spouses) have reported their emails were used in just this way.
There's more where that came from, of course, but it is true that contact information can be bought bulk fairly cheaply. Hendricks also mentioned spite-listing, but you'd have to have ticked off a lot of people for them to take revenge by adding you to an AM list.
Hendricks mentions that at this point finding out if you're even on that list would require you to get access to stolen data, which you may want to avoid having on your conscience.