What does it take to be an expert? It's a good question for people involved in learning and development. After all, one aspect of our job is to create an environment, and deliver interventions, that helps to improve the performance of novices and experts alike. So we should know.
Luckily, researchers have been looking at this for the last few decades and we do know quite a bit. K. Anders Ericsson wrote a great article in Harvard Business Review a few years back summarising what we know about what it takes to become an expert. It's well worth a read (it's called The Making of an Expert). To summarise his summary, becoming an expert takes:
Deliberate practice with feedback - it's not good enough to just accrue experience; an expert deliberately seeks out feedback and applies their learning over and over again.  How often?
At least ten years or 10,000 hours - you'll have heard this before perhaps. The research conducted by Ericsson and his peers is where Malcolm Galdwell got his thesis in Outliers from. This is the amount of practice it takes to develop expertise.
Coaching and mentoring from an expert coach - importantly, however, a good coach will know when to let the budding expert 'leave the nest' and coach themselves.
So all you need is to spend several hours a day for around ten years practising the thing you want to become an expert in with the supervision of an expert coach. Easy.
Here's the important part for learning and development professionals. After all that practice, all that time spent developing expertise, an expert no longer thinks like novice or even a journeyman. In fact, the way that experts store and retrieve knowledge is so different that it's unlikely that they know how to pass that knowledge on in a way that's easily digestible. So much of what an expert knows is encoded, tacit knowledge. 
This is, of course, where we come in. Learning professionals have long had the task of extracting key expert knowledge and producing a learning intervention that novices can then use in a practical way. We're never going to move people from novice to expert in a condensed time period. However, we can get people from novice to competent and provide them with the support they need to reduce unnecessary mistakes. 
So, experts organise their knowledge according to different principles and in quite different ways from novices. Why then would we turn to an expert to design the layout or structure of an online resource? Who is the resource for? Not the expert; they have all the information they need either on hand in their memory, or in their extended professional network.
It's the novice we should be designing for. And to do that, the best thing to do is find out how they would look for the information and how they would organise it. It's what Amazon does when designing its online store, it's what organisations with award-winning intranets do, it's what we do when we design our online management portals. Of course some guidance is needed, but that's only useful if the learner can get to the starting point.
The curse of the expert when it comes to online presentation is that they often decide they know better and produce a design that matches their own knowledge map - totally confusing the user. IT experts design the IT part of the intranet, HR experts design the HR part of the intranet, product experts design the product information parts of the intranet and all express surprise that users never seem to use them.
Ignoring the impulse to employ your expert knowledge and change something because it 'just makes more sense' from your expert point of view is a difficult skill to master, but it is important if you want to help people learn more effectively.
 See also The Role of Deliberate Practice in the Acquisition of Expert Performance, Ericsson et al.
 There's a great chapter summarising much of the research in this area in How People Learn: Brain, Mind, Experience, and School, by the Commission on Behavioral and Social Sciences and Education. It's only 19 pages and it's absolutely fascinating (for a learning and performance obsessed geek like me).
 It's worth noting that true experts don't need our help in the domain that they have their expertise, and a good amount of research also shows that experts know better than most where they are lacking the requisite knowledge and skills to carry out a task in a domain that is not their own. The key is that not many people are really experts, and so most do need help. However, experts learn best through informal means: for them, formal learning is 'background material'.