When posting an ad I have had no luck, even when I was dating someone and I was looking for a third woman or couple, nada.
However, when Aquafeline posted (I think it was personals) many a year ago about finding a place to live and meeting people I did reply. I met her, played with her, and eventually dated her for about 9 months.
It is not hopeless. However, yes the 1 line sentence of "where are you ticklish" or the like is a turn off for anyone. You want to write something that lets you get to know the person without spending 30 min on it only to be ignored.
To the men and women out there... if someone writes to you POLITELY you should at least give them a reply of no thank you/not interested vs. just ignoring them. That is just rude in my opinion.