I have told everyone I know and especially anyone who cooks for me, it never really occured to me to not tell anyone. My mother thinks I take it far too seriously - she is type 2 herself and can happily chomp on chocolate, cakes and sweets. I do have acces to her NHS records and can see that her last test showed 42 and her eyesight has never been affected, unlike mine.
Sadly my wife (now my ex) didn't take it seriously at all and would constantly cook carbs in every meal and moan when I kept having to say I just can't eat it. She was a bit controlling and just blamed me for getting it, whenever she was ill (complete drama queen) I did so much for her and when I get ill she did nothing for me, haha.
My friends and other family also know, and people do tend to ask questions and I'm happy to answer them all. People who haven't seen me for a while tend to ask why I've lost a lot of weight and I tell them I have a chronic disease, haha. Newer friends tend to not understand why I have got it as I am now the right weight but I don't have any problems explaining it to them.
If I still worked I would certainly tell them about it. I did indeed work with people with both type 1 and type 2 and no-one ever gossiped behind their backs or anything that so I wouldn't expect anyone to really. I think it's a good idea to let work know just in case of any medical issues that arise but I guess it does depend on your workplace - I used to work for the NHS and wouldn't have a problem telling them.