Or never shop with any company that
uses Internal facing microsoft servers.
As if.
Everyone has room to raise their ethics quotient here.
You're making a hell of an assumption: no one said that the servers that were breached were Microsoft.
The only details of the breach that have been released thus far have been that the Point of Sale systems that Target used involved using customized (in-house) developed software running on top of Windows XP Embedded POS.
Now if you're saying "don't shop anywhere where Windows XP Embedded POS / OS is used" .... good luck with that. It's (unfortunately) one of the most popular platforms for POS systems.
A better position to take might be this: If you're out shopping and want to remain completely safe from credit card information theft ... pay cash!
Best carry a gun with you too while carrying that cash ..