eBooks certainly have the advantage of storage space & portability, but the only way to read nook ebooks is in the nook app. Ebooks are more geared to novels (as opposed to foreign language workbooks or puzzle books - those types of books I still prefer "hard copy" books).
There are ways to "future proof" your ebooks - Google or your favorite search engine is your friend here - but those ways are in a legal grey area. If your truly worried about Barnes and Noble getting out of the ebook business, you might consider one of the other ebook vendors that uses Adobe DRM (ie Kobo, Google) so you can read it on any software/hardware that uses Adobe.
jaquellae's answer is nearly identical to my own. I also have/had a vast collection of "real" books, but they are just not convenient in small spaces or when moving (more boxes of books than clothing, bathroom items, and even computer stuff combined). eBooks are more or less terrible when it comes to foreign language (Japanese fonts are especially awful), math, and detailed diagrams (even though you can zoom in many cases), but other books that are text are much more convenient. And you can't beat the portability. If your textbooks have formulas, foreign text, or detailed pictures, I recommend you get them in hard copy even though the prices are outrageous. If they are text (philosophy, English, etc.), I would recommend getting an electronic version.
As for worrying about the cloud, there are a few notes. First, B&N just sold off its video section, but those videos were not lost. They were transferred to another company. And just as B&N did when they acquired Fictionwise.com and eReader.com (one of my favorite eBook sites), I would imagine the eBooks you have will transfer to whomever acquires B&N when/if they go under. Second, this is one of the reasons I recommend getting a non-Nook tablet rather than a Nook tablet. You may be able to get a Galaxy Tab 4 Nook with the Nook software on it, but if B&N goes under, you're stuck with an interface that is obsolete. If you get a "generic" Tab 4 (or Nexus or whatever), you are not stuck with what may one day be an abandoned interface but can still load the Nook software, Kindle software, Kobo software, Aldiko (my personal favorite), or whatever. And yes, I know you can do that on the Nook tablets now, but again, you're getting a Nook-centric tablet that is not future proof. And speaking of future proof, jaquellae is right on that as well. Do a search on the term (or just look up Apprentice Alf and Calibre), and you'll learn all you need to know. It's not 100% future proof, but it works.