So I'm listening to my brother who was told and has now adopted the opinion that you shouldn't tell sexual partners about your STD/STIs. His friend (a woman!) has crotch fleas and doesn't say anything. She sleeps around, which whatever makes you happy, but to do it with some thing contagious?? Are you frucking serious? I told my brother exactly how fucked up that it and he says "well how are you supposed to get laid?" You don't, nasty fuck!

Am I nuts? Should you TELL people you have something?

And no it doesn't "depend on what it is" if they have the tiniest chance to catch it then you should tell them. If you can use prevention fine, but they should know there's a chance!