If MS really tries to close the market of Windows on PC, it will be its worst mistake ever, and probably the first deadly one too. Many huge new markets grew outside of PC, and by now their user bases outnumber Windows, and amongst them there is a big, quite open one, Android, that would be SO glad to fill the place for an open market on PC, should MS make Windows closed. The risk for Windows PC if it gives up one of its strongest features, is marginalization.

But that's not what they're doing.  This only has to do with the Windows Store.  So what's the problem?

In fact I wrote "if". But you too know that there are some people at MS that would like it, thinking they still live in times when it would give the company more power, instead of isolating it. The problem is simple, if they tried, they'd have their fingers burnt, but in the short term their users too would be harmed, so we're just trying to exorcise such a possibility. Also, it can be a good idea to let MS know, through reactions on the net, that this isn't a good idea, just in case some high execs think the opposite, better safe than sorry.