I never thought some thing would be a challenge for ASK TOM Team and i thought plsql developer job is like a peeling banana for ASK TOM.
but i realized one thing after reading this question is, Challenges and hard work made ask tom team to be Expert in Oracle Database. people like me and others have interest and lot of curiosity about Data bases and Other Technologies, those are like a ocean we can not Explore every part of ocean until we explore every part by swimming,situations make us to swim in a specific area, in Our technology ocean Challenges and requirements are like situations those will make us to think about logic and make us to explore new concepts etc.
working people may get challenges but students and absolute beginners gets only resources to learn technologies and some hands on exercises. The Oracle Resources are good but those are like tricky to the Absolute beginners. i am following chris saxon Lessons data base for developers. those are good but my suggestion is just add some info like what knowledge should have before learning this lessons also some challenges which will make the learners to think out of the box.