I find LinkedIn immensely useful for finding out who works in certain roles at certain companies, then reaching out to them directly, say on Twitter, to report

I find LinkedIn immensely useful for finding out who works in certain roles at certain companies, then reaching out to them directly, say on Twitter, to report a bug in their software. It's been a proven strategy that works time and time again compared to the void that eats up bugs reported to large companies (if you can even figure out how to report one).