Sentence:  Since the launch early last year of [...] two Silicon Valley start-ups offering free education through MOOCs, massive open online courses, the ivory towers of academia have been shaken to their foundations. University brands built in some <WSD>cases</WSD> over centuries have been forced to contemplate the possibility that information technology will rapidly make their existing business model obsolete. 
Meaning of the word marked with <WSD> tags:  An actual event, situation, or fact.