...I think the risk that microsoft starts blocking installs for no apparent reason is very unlikely.
.msi files are standalone installers which do not need network access so I cannot see how Microsoft could block them even if it wanted to. Again, might you be confusing web-installers (
examlple for DX9) which scan a system and trigger a second download with redistributables (
example for DX9) which don't?
...Even less likely than Valve going at of business.
I'd agree that the prospect of Steam going out of business is not likely (short of the catastrophic security compromise scenario mentioned above). But that's because Valve can start imposing fees (per year or per month) to keep accounts open instead (with 65 million accounts, a $10/month fee could pull in an extra $6.2
billion annual income even if only 80% of users sign up).
...there are already third party steam-clients that allow installation of your ... uhm .. backups.
Good luck with that - a online search showed many sites claiming to offer such software just redirected to third party downloads where you had to complete a "survey" first. And one which did provide a download with
these malware scan results.
