Hmmm... I have Horizon plus additional plugins (SSL, etc) on my main tower and Diamond plus additional on my laptop, all under the same account, and have used Waves for 4 years. I've done some upgrades in the past (and got the vouchers and used them), but also held off on several upgrades for stuff I now don't use. When v10 came out which is a major upgrade, I did WUP for those things on a few separate plugins, but also used a bunch to just get up to Horizon so all that would be in v10. I haven't lost anything, my older v9 are still there and usable if i want, which I usually don't. Nothing is lost.
I don't mean this to be a "hey, what are you doing wrong" reply, but I will defend Waves that they are not a scummy company looking to rip people off and therefore requiring us to seek out a trade commission, like was said at the start of the thread. They are trying to survive in a very proprietary market that doesn't exactly catch the attention of most households in the world, like food and cleaning product companies do. TBH I didn't read every reply so maybe this reply is a day late and a dollar short... if so my apologies.