Lack of sitewide https
I signed up recently. The registration lacks https and therefore you're basically leaking your password to middle man. Also for password, special characters such as ~!@#$% are not accepted, something I rarely see elsewhere.
The admins currently know about this and are currently working on an update to the site to address this issue.
If you have any further concerns, please submit a ticket to Support at http://www.funimation.com/support.