The term that bugs me is "bandwidth" when what is meant is "data capacity". Bandwidth has a specific meaning, and it is NOT directly related to data rate or data capacity at all. (More efficient encoding methods and modulation techniques can squeeze more data into the same bandwidth, while inefficient encoding and modulation methods may use far more bandwidth to carry a lower data rate).
But I've gotten used to hearing that term used to mean data rate, and I guess it really doesn't matter except that it can become misleading, and really confuse people when you DO try to discuss data transmission methods, radio work, optics, filters, etc. Then it sucks to end up with one term that has more than one possible meaning. So effectively, a once-valuable word has been made less useful, or even ambiguous.
Still, that's just how language tends to evolve.
It's like the word "momentarily". When I was a kid, that word meant "for a moment", and you'd have points taken off if you mistakenly used it to mean "in a moment". But now, it's been misused so much that it's common practice to hear show hosts say "We'll be back momentarily." even though they really mean they'll be back "in a moment", not "for a moment". And I believe at least some dictionaries acknowledge that this is now considered "common usage". But again, while it seems inconsequential, the fact is that we've lost a formerly valuable word because it can now have two meanings. And if we want to say "for a moment", we have to write it out or say it that way, because "momentarily" no longer has that unique meaning. So in my opinion, the language has been "damaged" by accepting an improper definition.
I don't think that same issue exists for "footage", though. I am not aware of any common cases where a person has to go to extra care, and purposely avoid using "footage" because of some ambiguity that it has taken on. So it still seems to be a valuable word.
If you look into many words, you'll find that they have their origins in some meaning that they no longer have. Some of this evolution is good, and some is bad, in my opinion.