Just the other day, I wrote about naming (or is that defining?) a product category. Today, Chris Hoff takes on SaaS vs. Cloud SaaS. Now, it is fairly common to take on these types of exercises - I have done this a number of times myself, for example with Rootkits and Zero-Days. But I have to say that it often seems like we spend all this time for no particular reason more than to assert that we are "right" and someone else is "wrong."
The real reason to care about definitions is to ensure that there are no communication difficulties between multiple parties; that folks know what each other is talking about. Secondarily, there may be a need to distinguish various characteristics, etc.
At an even broader level, it is useful to ascertain at what level this matters. There are no "facts" in definitions, because we know for certain that definitions change over time - sometimes in subtle ways (when did "omen" begin to incorporate *good* luck?), but also in more obvious ones.
Since turnabout is fair play, it is worth questioning why I care so much about this topic (I've written about it a few times over the years). I don't have an answer for that, except to suggest we spend a lot of time on "meta" and not enough on "meat".