When the correct items for crafting an item are added to the interface, the resulting item can be crafted. If you haven’t previously crafted that item, you discover the recipe for that item, allowing you to easily view the correct combination to recreate the item. Some basic recipes are automatically learned by characters, but the recipes for most items must be discovered by the crafter.Unbeknownst to ArenaNet somebody already developed a sneaky technology which is designed to thwart this sort of game design. It is called "the internet". The kind of puzzle that is finding all valid combinations of a limited number of resources is best solved by brute force, and is done fastest by crowdsourcing, many players working together on a Wiki. Before Guild Wars 2 is even released, all possible recipes will be already available on some such site. Thus every character with that crafting discipline will be the same. Objective failed!
We decided to go with a discovery system for learning recipes so as to allow crafters to distinguish themselves. When there is a static list of recipes learned from a trainer, every character with that crafting discipline is the same. However, with a discovery system, players that spend time and effort on their crafting disciplines have a way to distinguish themselves.
So what could ArenaNet do instead? One system that can't be killed by some internet database is recipes being discovered randomly while crafting other items. Every time you craft an item of level n, you have an X% chance to randomly discover a recipe for an item of level n+1, and so on. If you want every crafter to be unique, you have a cap of how many recipes of every level can be discovered, while having at least twice that many recipes in the game. Thus every crafter has a different random set of recipes in the end. Of course that means that some people will be luckier than others, and get more desirable recipes, but that is the price you pay for not every crafter being the same.
Theoretically one could make a game in which random recipes that are different for every crafter are combined with the kind of combination style puzzle ArenaNet is planning. Two people using the same combination would get different results. But given a limited number of recipes that would also mean that two people crafting the same item would use different resources, and thus have different costs. Not a good basis for a player-run economy.
The game which solved crafter differentiation by far the best is Star Wars Galaxies. Everybody had the same recipes, but the quality of the items produced depended on the quality of the resources used. The difficulty was thus in finding the most high quality resources, the location of which randomly changed every week.
But sorry ArenaNet, a system which is based on combination puzzles to uncover hidden information doesn't work well when players can exchange that hidden information. You have to do better than that.