I remember once reading a bank's FAQ trying to explain why passwords couldn't contain SELECT, UPDATE, DROP, or DELETE. I can't find it now so hopefully that little problem has been fixed...
One day she told me she always had trouble remembering which way to log in... which seemed strange to me. Anyway, her surname is Irish, one of your typical O'Somethings. When she tried without the apostrophe she was fine but when she used the apostrophe it failed with a SQL error message.
When I finally was able to breathe again she asked me what it meant. I just told her that it meant that she should never leave any money in that account...
One time I gave feedback to Google, from a Google feedback form, and gave my real (and had been in use for years) googlemail account name on this Google form.
The form rejected it, because my real name has a mild swear in it.
That kind of thing is vaguely disappointing.
I did suddenly have to change all the answers to my 'secret questions' when I realised that I'd have to read them out loud if I needed to get back into my bank account. Lots of profanity snipped there.