Former CreateSpace publisher here. CreateSpace has purchased a large block of ISBNs, which it "recycles" among its books: if you publish a book, then stop publishing it, it will be reused for someone else. They also don't update the ISBN even if you radically revise the content of the book. Needless to say, this wreaks havoc with 3rd-party inventory systems that rely on the ISBN on being unique... although in my particular case, it saved our ass!
I'm not sure that's true that CreateSpace recycles its ISBNs. I haven't seen a credible source discussing this, and it doesn't make sense to me. ISBNs are cheap and it would be a pretty gross misuse of the ISBN system (which are supposed to be unique even across different formats of a book).
It may be that they will "recycle" an ISBN if you start the process with them but never actually complete the publishing process.
http://gyrovague.com/2012/12/18/wikitravel-press-seven-lesso...