There are three broad types of key switch: clicky (makes a loud click), tactile (tries to feel like there's a click but be fairly quiet), linear (no feeling except gradually increasing resistance).

There are also silent versions of tactile and linear switches.

Clicky switches are inappropriate in every office, and silent switches may be preferred in a particularly quiet office. Typical keyboards (Dell, Apple) fall somewhere between the tactile/linear and silent switch mechanical keyboards.

I work in a lab where most people have mechanical keyboards (including myself). Yeah, it's a little noisy, but that's nothing compared to the volume at which people talk, and how they frequently have simultaneous unrelated loud conversations within the same small space.

I agree especially because I use a mechanical keyboard as well, and it makes convincing someone to bring it more difficult. Some folks are really unreasonable with the sounds that they expect others to not be able to hear, and I think it ruins it for the rest of us.

You haven't heard a VT100 with the keyclick on then or a IBM Selctrix :-)

A machinal bucking spring keyboard is not that loud compared to the average open plan office.

I've banned such keyboards in my office (open space) and I've heard about some coworking places that banned them as well.