The basic premise of Pinterest is that its the electronic version of the old cork boards. When you used the old cork boards, you'd clip a picture from a magazine and pin it to the board...as in, I want those shoes! With Pinterest, you do that same task electronically when pinning but you can pin to many different boards.
Right now I have one genealogy-related pin board...and it's a mishmash mess. If I were seriously going to use Pinterest for genealogy, I'd have to take a good look at what I would do with the boards. Since Pinterest allows you to create lots of different pin boards, I might have a board devoted to my blog posts that I've pinned...My gen blog ramblings. In addition, I might have a board devoted to pins and repins from newspaper websites...My obit sources. Also, I might have a board devoted to pins and repins from blogs with methodology that I want to try...My new gen methods.
Since you can have as many boards as you want, why not sub-divide boards so that they reflect smaller areas of interest...and when you get lots and lots of pins and repins, allow you to find what you're looking for on your own boards!
Can you tell I'm having a good time on Pinterest?