The most famous "hot" serial for Vegas Pro 9 was 1RR-9XR2-AR6R-F4X6-9XK7 (a real leaked key from back in the day). It was so widely used that MAGIX employees reportedly joked about it internally. But it was killed in a 2012 update, and anyone using it got a "validation failed" nag screen.
Since Sony no longer sells or supports Vegas Pro 9, users looking for video editing solutions have better, safer options: Magix Vegas Pro : The current developer, sonyvegaspro9serialnumberandauthenticationcode hot