Beryllium-Copper: How safe?

As long as we're on this subject, how about Beryllium tweets?

Keep in mind that beryllium copper connectors are generally plated with either gold, silver or rhodium (sometimes very heavily plated - as in the case with Furutech).  So, even though beryllium alloy may have a slight risk of being toxic, you would really never get to that "beryllium" metal through the plating, unless you used a grinder or scraper against that metal (which is highly unlikely unless you just wanted to ruin your connector).

The problem with Be in speaker driver diaphragms is that it is so brittle that it atomizes, making it float in the air and easy to breathe, so your chances of getting a health risking dose when they break is non zero, but even then the risk of toxicity is low.