I know about that, oh yes I do. I had a girlfriend who I sometimes said tickle threats to, by text message or in telephone conversation.
One day when we were on the phone, I told her : "tonight, when you'll come over at my flat, I'll catch you, strip you naked and tickle you like crazy. I'll make you be a little girl again, and you'll be screaming with laughter !". She giggled at my words. And when we woke up the next morning, I kept my promise and made her scream with laughter like a tiny baby ! And while I tickled her, I was saying things aimed to make her lose control even more, like "Aaaaaw, is my little baby doll a little ticklish ? Aawww, that's sooooo saaad....." Adding things like that made her even more vulnerable. Needless to say, we soon made love afterwards. Frequently I was telling her silly things, like "tonight, the horrible tickle werewolf will tickle this little girl and then totally eat her from head to toes, like the hungry monster he is !" To my, tickle threats are a important part of the tickle experience. It seems to make ticklish girls even more adorable than they already are !