Here are a few challenges I've started tossing out to prospective new hires, all of which are based on common, real-world multimedia tasks:
I learned this the hard way over the last four years. When I started working with ActionScript in 2007, it was the first serious programming I'd done since college, not counting some playful Excel macros. Consequently I had a lot of bad habits: I left a lot of variables in the global scope, stored data in ad-hoc parallel arrays, and embedded a lot of "magic number" constants in my code. Some of those are easy to correct, but the shift in thinking from "write a program that does X" to "design data structure Y, then write a program to operate on it" is surprisingly profound. And yet it makes a huge difference: when we created the Economic Indicators project, the most problematic areas in our code were the ones where the underlying data structures were badly-designed (or at least, in the case of the housing statistics, organized in a completely different fashion from the other tables).
I suspect that data-orientation makes for better programmers in any field (and I'm not alone), but I'm particularly interested in it on my team because what we do is essentially to turn large chunks of data (governmental or otherwise) into stories. From a broad philosophical perspective, I want my team thinking about what can be extracted and explained via data, and not how to optimize their loops. Data first, code second--and if concentrating on the former improves the latter, so much for the better.