I'm not really a perfectionist when it comes to my professions (and I'm definitely not the type who would announce such accomplishments in a public forum), but I have known other people that were. One guy I know is a blacksmith and spent hours researching and tracking down every last pattern that was available to him. The same guy was making a point to complete every single available quest in the game too, so his blacksmithing goal wasn't really his loftiest.
Personally, I tend to be more utilitarian. If I can't use an item in some way, then I don't care about learning how to make it. Of course, I have a relatively broad definition of "use", which includes giving away items to friends, making money on the auction house or simply earning skill points. I've only rarely gone out of my way to pick up recipes, and only when I had a definite plan to use them.
How about you? Do you spend a lot of time and money tracking down rare recipes even if you'll never use them? Or are you more like me when it comes to such things?