Well, isn't Microsoft stealing from people too? I mean when you buy a product what gives the company right to come to your home, disable your product so that you are forced to buy the newer model?
They don't do that. If you have an old computer running XP today then it will still work in the future. Although it is the first OS that had to be activated online, so it will be interesting what they do about allowing new installs.
They might do what Adobe recently did with Creative Suite 2 and put out a new version that no longer requires activation.
Providing security updates is another matter.
I never upgrade the OS on an old machine. I get a new machine designed for the new OS. I can't give up Xp because I need it to run my very expensive printer and scanner combo that isn't supported beyond Xp. This qualifies as a business use. I will be running print jobs with Xp long after 2014 barring natural disasters destroying everything I've got.
My five year old laptop came with Vista, I upgraded to 7 and now 8 & it runs fine. Old hardware can be a problem, as long as your hardware came with a vista 32 & 64 bit driver then it's likely to be supported by 7 & 8. But hardware from XP or earlier can be a problem, I used XP mode for testing some old hardware before selling it. Driver support in Linux or MacOS is worse though.