BTC-Arbs.com has not shown a single piece of evidence that there's actual trading going on. No contact information (other than email) either.
Hmm.. Do you know their email? Has anyone ever got an email from them? I only communicated with them through the contact form on the site.
Also beware of forgetting your password. If you happen to forget you won't be able to reset it - they(he?) ignored 4 support requests to restore password for my (second) account.