I've used computers for over 45 years so I've seen my share of computer programs, and computers, come and go. But it's always discerning when long used programs go away. Of course data stored in proprietary formats is the riskiest problem. But the effect on one's workflow is also an issue. I think that now that I am retired, and older, it's becoming particularly irritating. So here are some issues I've had and am having, personally.
I've gone from IBM 360 (and punched cards) to DEC PDP-11 to TRS-80 to CP/M to MSDOS and Windows with a stint using OS/2 and now for the past 9 years the Apple Mac. Luckily I had no investment in Power PC Mac programs. Each of those changes has generally meant a complete change of application software and more often than not new file formats. I'm concerned about changing again. If Apple goes to ARM processors, that would be another change which would be difficult because of my reliance on discontinued/abandoned software that only runs on Intel Macs. And, of course, this software could still fail with future OS versions.
I started writing programs in Java in the late 1990s. I used IBM's Visual Age for Java, which was the most advanced IDE at the time and in many respects the most advanced IDE ever. I can still run it on a Windows 2000 virtual machine, but it is locked in to an old Java version. IBM abandoned the product (which was actually written in Smalltalk) for Eclipse, which I've never liked. I was making major use of Java Beans which was well supported in Visual Age, but also supported in Borland JBuilder, so I switched to Borland. But then Borland also switched to Eclipse. So now I use NetBeans, which contrary to the name has minimal Java Bean support. Now things went from about $100/year to free, but the quality and power is much reduced, so I'm not a happy camper. Luckily Netbeans is cross platform (I've used it under Windows, Mac OS X, and Linux) and still being developed and supported so I don't feel that I will be orphaned again.
Nobody has ever been fired for buying IBM, but this doesn't extend to their home products. With Visual Age the product was originally low enough priced for non-corporate users but the successor was much more expensive. I was also "burned" by OS/2. I also has a good website design program for home users that they abandoned. And they also abandoned a tape backup program for OS/2 before they abandoned OS/2. Basically every IBM product I ever bought ended up being abandoned.
When I first went to digital photography I still was Windows computer based. I used ACDSee and Photoshop Elements. I kept my image files in a folder hierarchy. When I went to the Mac I bought Photoshop and used Bridge for management, still keeping the image files in a folder hierarchy. Then I got hooked on Aperture, now abandoned. I'm still using it, but keeping the image files external in a folder hierarchy. I'm not happy about Aperture being dropped as Photos is not a substitute and I don't care for Lightroom. I also use the Nik plug-ins which have become free and certainly will be abandoned as well. This leaves me in a waiting game. I save the processed images as large JPEGs, larger than I would otherwise need, so that I hopefully will never have to reprocess images with another program. I do keep all the raw initial images just in case. Luckily even those from my first DSLR, a Nikon D70, are still readable.
Luckily the oldest documents that I wrote and care about were printed, and I've scanned and OCRed them. ASCII text files, if I still had them around, would of course still be readable and the first word processing files I used where nroff format which is still viable! But with the move to personal computers I used a sad sequence of now dead word processors -- Superscripsit (TRS-80), Wordstar (CP/M) which is actually fairly recoverable, PC-Write also fairly recoverable, some really nice word processor for OS/2 which isn't recoverable, and many years of WordPerfect which can be read by LibreOffice
But problems came after I switched to a Mac! No WordPerfect on a Mac and I don't like Microsoft Word after many bad experiences in the 90's. So I embraced Pages. This has been precarious since the latest versions were de-featured to match the iOS version. Until recently the latest Pages wouldn't even open the earliest Pages documents. Luckily the older Pages '09 continues to work. I still use Pages but have added Nisus Writer. The advantage of Nisus Writer is it's native save format is RTF which will open in just about everything (but Pages!). Nisus Writer is also fully OS X featured while LibreOffice/OpenOffice.org/Microsoft Word are not.
I've been a big user of Circus Ponies Notebook. The company suddenly closed its doors. I'll continue using this program but it's proprietary document format is a risk. Luckily the document content can be extracted.
What's next? I should be suspicious of programs from small companies, but so far the failures seem to have come from large companies' products (except for Circus Ponies). Obviously programs which have proprietary data formats, such as Scrivener, pose the greatest risk. I've used the Epsilon programmers editor since the late 1980's and it's a 1 man operation. Sounds risky but since it only edits ASCII text files I don't really have to worry although I'd sure miss its absence.