I think it’s a fun idea, @jasonreilly but I have to say, I would find it daunting unless you gave some really good clues about where it might be.  Especially if you have a blog with lots of blog posts.  Some people don’t know how to navigate through old blog posts.  But I would be interested to hear from others if they have tried a contest like that or entered one.

Hi Jason, 

I hope you find this of help - 

Unless you have a lot of traffic or offer a very good price I would not recommend these kinds of mechanics.
From our experience, if the user has to perform some action outside FB, or in other words, the FB flow gets interrupted, the registration falls dramatically.
From a technical point of view, it is quite easy to do. How? 
1. Choose Easypromos premium. Why?     1.1. the promo admin can customize the registration form with your own questions.     1.2. the promo admin can choose ‘multiple entries’, it means that the user can enter the competition more than once. 2. Every week or every day, the user has to answer a different set of questions based on the clues he will be finding in the external website.3. When the promotion is finished, the administrator will have an excel file with all users&answers.4. The winner is selected among those user that have answered all questions properly.  
Easypromos is at http://www.easypromosapp.com
I’m happy to be of further help.
Brian