I'm as stealth as I can be, and only out myself if necessary. Can I say for sure nobody will ever out me? No. Do I expect that no one can find out about me? No. Realistically I'm as stealth as I can be, but I, unlike Myles, am out at work, though not sure if all of the newbies know, so I've stopped talking about stuff there, and I'm out to family and friends who need to know. I have 'reintroduced' myself to people I don't wish to out myself to. I just pretend I don't know them and start over. Much easier, esp. if there was no connection there other than acquaintance.
Case in point: former client from when i had a business. She works at a local office that I go to infrequently. I ran into her there at the start of my transition (hair cut, androgynous clothing), but as time went on and I went very infrequently, she no longer recognizes me at all. If I had to speak to her (haven't had to, but she's glanced at me with zero recognition, and we used to be really chatty!) I'd not out myself. No point, really.
Jay