The noise is from bottoming out. Put spacers on the keycap stems, and it stops being a problem, no matter what kind of switch you use.

This is easy to do and only a little time-consuming. It's easier and faster when you take a cheap Bic pen, pull out the tip and ink tube, and use the body tube to press the spacers down on the stems - it's just the right diameter, and makes the job much faster.

The spacers are cheap, too, being simple silicone rubber O-rings, and as an extra benefit, the rubber eats up a lot of the bottoming-out force that'd otherwise be transmitted up the key into your fingers, which means you type more comfortably as well as more quietly.

I'm a nice guy, I paid the extra $$ for silent mechanical keys (http://matias.ca/switches/quiet/) ;-)

In my opinion, if you know you're going to be working in an open office setting, you should try to be courteous and minimize the negative impact you have on your coworkers. I think you should be willing to make the choice to use a quieter keyboard that isn't necessarily your favorite.

So I'd say the problem is with both. The open office is the ultimate source of the issue, but it can be compounded by workers who make choices that exacerbate the situation. The reality is that an open office can be quite pleasant if the people working in it collectively make effective choices that take into account the well-being of the group.