Finger firmly fixed on the pulse of SciFi fandom, io9 asks, "Are bookshelves becoming obsolete?" Seems to me the question is more, "are paper books on their way out?" and I can dispense with that questions quickly with a simple, "yes."
I am convinced that ebooks have won. There will always be holdouts and it will take a long time for paper books to get to where vinyl records are now (temporary hipster renaissance), and then eventually where wax cylinders or clay tablets are (museums only), but there's simply too much for readers, publishers, and authors to gain from ebooks. I've covered this ground before, and I may again, but let me indulge in a little sappy nostalgia (again? yes, again.) for what we're losing.
Your taste and knowledge on display
I've heard that ebooks are enabling a resurgence of smut because you can buy dirty books in private and read them in public without having to hide the cover. Hard to say if that's good or bad, but in the paperless book future, you won't be able to peruse your friends' libraries so easily when visiting their homes, and you won't be able to impress your own guests so easily with the size or depth of your own library. If you find yourself in a bookless home, you'll have to run off to the loo and peek into the medicine cabinet to get insight into your host.
Design and the nature of shelves
Owning, storing and displaying stuff creates constraints and challenges, but constraints and challenges also create opportunities for design and innovation. I won't miss packing, moving and unpacking tons of books. As a dweller in small apartments, I'd be happy to reclaim the space taken up by my paper books, but I'll also be sad to leave behind the design choices of bookcases. The Economist notes that IKEA redesigned the ubiquitous Billy bookcase to be any "anythingcase" unbound from the size and shape of books. I guess we'll always have bookshelfporn.
Every book for itself
No matter how many or how few, how fancy or how plain, your paper books are yours, and each one is a separate object that you can loan, sell, gift, even alter or destroy. Those books exist outside of Kindle, outside of iPad, outside of DRM, the internet, and electricity. Until the ebook world comes up with a satisfactory method for giving away or lending ebooks, maybe even inscribing them, I'll miss those possibilities most of all.