I'm just on my first period with my Divacup/Mooncup; I have both but I use the Diva most of the time. And I'm so enthusiastic that I have to tell everybody about it. So I thought, well, will I tell my parents, too? How will they react, and what will they say? In my family, there has never been much talk about the lust aspect of sexuality, but we've always maintained an openness about health issues, illnesses and so on. To give you an idea: I'd always talk freely about my latest YI or pap smear, but I wouldn't dare talking about any sexual issues. I always preferred doing this with friends. Anyway, I couldn't make up my mind whether talking about my Divacup was a good idea, so I decided I'll just wait and see.
Of course, my enthusiasm got the better of me, so I told them. I ranted and ranted. They asked - I explained. They wanted to know details - I gave them to them. It was totally cool and so relaxed! I sat there and thought, wow, I have some really cool parents! They are so IT:curious! And I felt so cool myself for just telling them about it, like "Oh, by the way, recently I made a great discovery." It was a really special atmosphere. I also told them about this LJ, and they thought it was fantastic that women support each other that way with tips, folding techniques, comparison pictures and so on.
After I had finished praising my cups, my mother told us about her first period and about the troubles and the discomfort with pads she experienced. She was about 12 at the time (early 1960s), and her mother's reaction basically was: "That's your period. From now on, you will get this once a month. Use this." And gave her pads. My mother said the pads back then had strings attatched to them (on the front and the back), and those strings were connected to something like a belt that ran around your waist. She hated it, and when she was 16, she switched to using tampons (she didn't know why her mother didn't tell her about tampons - if her mother hadn't wanted her to use them or if they simply hadn't been available back then).
Of course I wondered whether she'd try the cup herself. Well, turned out she's reached her menopause and doesn't need it any more. What a pity! But she said she'd definitely mention it to her colleagues, and she seemed quite thrilled about the idea of telling them something they probably haven't heard of before. :-)
We talked some more about sexual education, and I went home with a great feeling of what cool parents I have. Oh, and today, when they come over, they want me to show them my Mooncup!
EDIT: I just wanted to point out that I'm not living with them. I'm 31 and I have my own apartment. So my motivation wasn't like "I should tell them in case they find it", but rather "I'd like to let them know that I made an incredible discovery I'm really enthusiastic about". After reading your comments I had the impression I should have mentioned that before just to make the situation and my motivation clearer to you. :-)