Why does 500 Startups' www point here?

Thanks for pointing this out, we're working to fix this now.

It looks like they might have started using Torbit to speed up their site, and something go messed up in the process (either on their end, or on Torbit's). You have to change your dns settings to use it, so this seems like a likely possibility: https://secure.torbit.com/site-optimizer/technical

They seem to be using a reverse proxy web accelerator service/CDN similar to cloudflare bit it looks like they've only configured 500.co not www.500.co to go to the correct backend.

It's a name that was reserved by the .CO registry. I don't know if they are hosting the website as well, but I have contacted CoInternet to suggest they address the issue.

Hey Thanks all! In touch with 500.co - and they are on the case. @DotSauce - thanks for letting us know! -Lori.co

aaaaaand it's fixed.

because www.500.co is cname'd to 500-co.torbit.net.