Yes please!

Last year, I discovered a severe security flaw on a couple dozen websites and the sheer communication of this was super painful. I can't just e-mail someone at hi@foobar.com, I'd usually have to send an e-mail along the lines of "Can you give me a contact for your admin/security guy? I have something here and I can't quite disclose it just now." The response rate was extremely low.

If you just give me a security.txt, at least I know I can disclose something and I have some level of certainty that the e-mail will be read.