To those who say they don't understand, this is simply a combining of two fetishes - a tickling fetish and a cuckold fetish. I've never heard of a woman having this, but there are men who are very aroused by jealousy. A willing girlfriend or wife will have sex with other men to turn on their partners. I remember the movie Sideways depicted this in one scene - but it had nothing to do with tickling. Combining the two is rare - me, this guy and about six other people seem to be the only ones. In 30 years I've only read one other story that depicted this scenario.
I have to agree that the story is pretty hard to believe. It's not easy to pull this off, and the convenient, fetishist ex and the video all sound like the stuff of far fetched fantasy. Nonetheless, this theme so rarely gets any press that I was really happy to read it. True or not, thanks for posting it, my friend.