How robots and spiders are causing issues, how to stop them. We can also talk about Completely Automated Public Turing Test To Tell Computers And Humans Apart - their use, their compliance issues, porn proxies, PWNtcha and other ways to defeat them.
First there's the really really annoying (and illegal, in the UK) fact, that there's no alternative offered for visually impaired users (this could be solved by the implementation, but there's nothing built-in), it also relies on javascript which is also annoying.
I'd also like to see how the 'ticket' system works, and whether a ticket could be used more than once, etc. I think the devil here is in the web site's implementations.
ALSO.. the 'adopt me' link takes you to a page about the animal in question... this could be used to index the entire database in... assuming one hit per second (zombienet with a dead-drop database somewhere) you're looking at 3,000,000/360 hours ~833 hours to index the database in it's entirety... and indexing even 25% of the database allows you to keep refreshing the selection until you hit 6 you recognise with fairly high reliability.