CUBA gradually moves to GNU/Linux and Microsoft may not like it much. But at a higher level there is also an embargo and fear, so it's only natural to expect limited cooperation across the borders.
This issue is a very odd one: it's not clear that Microsoft was ordered to make this change, so what made the company decide that US-embargoed countries aren't worthy of Messenger? Why now? To my knowledge, other Microsoft applications and websites still work (and if they don't, it likely isn't Microsoft doing the blocking), so what makes Messenger special? It's actually quite disappointing that a large company as influential as Microsoft would make such a controversial move: Messenger is a medium for communication, and the citizens of these countries should not be punished from such a basic tool because the US has problems with their governments' policies.
Users in Cuba, Syria, Iran, Sudan and North Korea no longer have access to Microsoft's Windows Live Messenger
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Microsoft wouldn't comment on why it chose to shut down the service at this time, or how long people in those countries had been able to access Windows Live Messenger. Microsoft said it does not currently do business with those countries.
Microsoft Warns Of SharePoint 2007 SP2 Glitch
Microsoft has discovered a major bug in Office SharePoint Server 2007 Service Pack 2 that renders SharePoint inaccessible after 180 days, and the company says it's working on a hotfix.