They do indeed discontinue windows just different versions of windows. What happens when XP suits you just fine but Microsoft decides that it costs too much to keep the activation servers running and you want to activate your legit copy of xp on a new machine. You are then forced to either:

1) Break the law and crack it. Doing this you will not be eligible for the updates that are there. In cracking it you are going to run a program that probably contains a virus/rootkit/trojan/whatever.

2) Reinstall the os every 30 days to bypass activation.

3) Need to buy/install a newer OS because you are at the mercy of a corporation with respect to DRM.

Amazon itself could shut down. If the recession has taught us anything it should be that we can't expect companies to be immortal.

If Amazon shuts down it means we've all been dead for weeks.