This is what the Feedback tab is for, which is present on all of the site's main pages. It should appear as a "clothes tag" on the left-hand edge of your browser window. WOWIO! employees monitor activity there and can pass any bugs on to the programming staff.
We also tend to get bug/problem reports in the forum's Help section: http://www.drunkduck.com/forum/9896/Generally from people who aren't sure if something is a bug or if it's just them/their setup, or who don't want to sign up for a Feedback account.