Plus what makes Anki awesome is the ability to use the cards on every OS, making it a ideal collaborative tool. But as mentioned by tom_b you need to create your own decks. There is very little use for most public decks unless you have the extreme lucky moment having to learn exactly the same as the author of the deck did.
In fact this might be a more interesting place for innovation - the management of Anki cards. Not sure how the market situation looks but you could be offering cards for popular textbooks or create a marketplace for these in order to rise the quality. Not sure how the copyright situation looks like, but you could be entering also a more mainstream market - for example by offering a card deck for each issue of Mental Floss in order to learn at least a few interesting things each month.
http://itunes.apple.com/us/app/ankimobile-flashcards/id37349...
If you can duplicate the benefit and make the UI simpler (e.g., simplify it down to two buttons: I got it right / wrong), and make it cheaper, you have an ok chance to do well.
I would suggest you create your own decks with images you find or create yourself rather than downloading existing decks. Memorization is generally improved by this approach (see Higbee, Your Memory : How It Works and How to Improve It).
I also like how Anki has spaced repetition built in nicely.