My friends and family all know about my knife hobby, and pretty much anybody who spends time with me will eventually learn about it. However, more than for knives, folks know me for always having tools, flashlights, a first aid kit, etc. handy.
I try to keep a low profile around people I don't know well, but not about knives in particular. I'm especially quiet around guys who seem to have a need to voice an opinion on topics they don't know very well (it might sound a bit pedantic, but I hate unsolicited advice).