Vendor Lock-in
In a 2014 blog post, Christian writes
On the other hand, one could say that as long as Microsoft exists, there’ll be a Microsoft Word. If Microsoft as a company outlives us, then we’re going to be able to rely on .doc files for our entire lifetime.
Well, last night I tried to open a Word file last saved in July 1998. This message popped up:
Clicking the link in the message leads to some "helpful" suggestions, like trying using TextEdit to open it. It then says:
So even the venerable Microsoft cannot be relied on. 
(By the way, I was able to open the file with an old version of Word.)
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