For the longest time, I felt like I'd never tell a soul. I too have felt shameful, and honestly sometimes I still do.
My girlfriend moved in with me about 9 months ago, and right before she moved in I was living alone. I had bought a couple packs of Bambinos and wore 2-3 times a week until she got here, at which time I made sure that I had burned through my entire stash. A couple weeks ago, I was feeling stressed to the point of being twitchy all day, which usually leads to what I would think to be mild depression. It used to be I would come to this website and read some posts, look at some pictures, read Adrian's blog, so I did again an noticed Bambino had a new diaper. On a whim, because my GF doesn't usually open my packages, I ordered a couple sample packs.
A couple days later, the package had arrived while I was at work and she had thrown it on the couch. I was sitting across the room, she told me I had a package, and she squeezed it, looked at it, and was about to open it before she decided to toss it over to me. What a scare! I opened the top of the bag, looked inside, and commented "Some airsoft gear, nothing exciting" and tossed it aside and went back to my computer. About an hour later we were discussing stress, change, and coping and I thought real hard about telling her about it. I realized that if she had found some adult diapers while I was away and she didn't have the opportunity to talk to me about it right away she would spend those hours constructing a totally false idea in her head. Either I had to be amazingly diligent in hiding this part of me (a 2-bedroom apartment isn't terribly big) or just come out. I told her, showed her a diaper, and put one on to show her. All super embarassing, but I knew I needed to make sure she had enough information about it to not let her brain turn me into some sort of creep.
My diapers dominated our conversations for a week or two, but eventually the topic ran dry and we don't really talk much about it anymore. She sometimes mentions that she wishes she had a stress relief object that worked for her like diapers work for me. I can wear one whenever I really like, and it truly is liberating to have a couple packages of diapers just sitting up in the closet with the rest of my clothes.
Overall, I think that the situation you are in should dictate whether or not you tell someone. I'm just a DL, and I only really have the urge to wear a diaper when I'm really stressed out and need to escape. Because I can go long periods of time without even thinking about diapers, much less wearing one, the only person I've ever felt the need to tell is my current girlfriend and I think I would have been worse off if I had kept it a secret. The questions I would ask myself if I was ever thinking about telling someone else would be:
Are they trustworthy?
Do they have a fair amount of opportunities to find out?
If they found out on their own, would it likely have a majorly negative impact on your relationship?
-How important is it to keep this particular relationship positive?
Would telling them, assuming their response is positive, greatly impact life in a positive fashion?
Risk and reward. With my girlfriend the reward outweighed the risk, especially considering the risk of NOT telling her was far more detrimental.