Should I trust bitaddress.org? AFAIK, the generation of the address pairs occurs on your computer but the concept still makes me nervous as it's occurring in the browser and I have to trust the owner of the site, I think.
You don't entirely have to trust the owner of the site. The site is client side Javascript based, which means you can probably save a copy of the code, then review it, and run it offline.

If you continue to use the website though, you're trusting the owner of the site to:


Not change the code in any way that compromises the security of the private key
Maintain adequate security so that no hacker can change the code in any way that compromises the security of the private key