incrediBILL - 2:28 am on Feb 4, 2013 (gmt 0)
Then you are blocking a huge amount of valid users. Almost all browsers can turn off referrers nowadays, plus the list I gave in one of my posts above.
Except most users don't know what a referrer is and barely understand a COOKIE. The mass populations often doesn't even know what an Internet Explorer or a Firefox is and thinks their Google start page is the internet.
I've been blocking images for blank referrers for many years without any complaints.