I don't feel it's unpopular at all! It's just that ticklers here, on most boards, at nest and all, are so uptight because it's sexual and they like to maintain that nothing is passionate or sexual about tickling for whatever politically correct reason.
In the group I'm a part of, breasts and gentials are tickled unmercifully as well as feet, pits and everywhere. It's all about the headspace and what you need. They even have a set of breast stocks there. On another thread here about tickling machines, I've seen them used on the breasts of a girl in the position I describe below. And this was also done to me in a similar fashion.
In private, lacing a girl to a post from ankle to neck with breasts exposed and some breast bondage applied really increases the sensitivity. The undersides are great to get, but don't ignore running a stiff feather directly over the tip of the nipples repeatedly. I've had my nips strung up and stretched tight and then a feather applied and it went right through me. This will make you so overly exited that any touch will tickle.
True tale! This was posted about on our group by the girl it happened to and others who were at this private theme tickling party. This is what I recall of it. At one of their parties (before I joined) guests were greated with a treat. The photos don't lie. The front door was modified into a sort of breast stocks. An unfortunate victim (actually she chose her own doom and wished this fantasy to happen) was strapped to the door on the inside right down to her fingers and toes tight up against it. Her breasts were thrust through the opening and exposed on the other side of the door. She had no control over them or herself. The 'master' running this event turned her into a human doorbell.
On the other side, guests coming up saw a large sign hung over the doorbell that said "Doorbell broken, please use knockers!" (love that touch). Lit by two small spotlights were her poor breasts awaiting god knows what. Alongside was a shelf attached to the wall holding an assortment of things you may do to them. Feathers, cold ice, clamps, ticklers and things to make you cream. Guests took full advantage of that knocker system. On the inside as she would start to scream, laugh and moan, or wail, they knew guests were at the front door. It was said that [the top running it] or anyone made any fast moves to open the door either. They let the human doorbell do it's work.
I absolutely love the combination there of the torture, the humiliation, the helpless breast tickling, the head space, and the humor.