If Barnes & Noble refused to pay (which is what Microsoft says), it's actually a matter of fairness that Microsoft enforces its patents because otherwise those who respect Microsoft's rights would be at a competitive disadvantage versus non-paying infringers.
Jeez Florian, you have come a long way since your campaign against software patents.
A few days ago you blow up the Bionic GPL issue as if it was an unprecedented tactic used by Google (and were soundly rebutted on LWN by the way ;) and now this.
Have you received funding from Microsoft at any point, perchance?