Unlike the early years, when Oracle clobbered a series of older, entrenched rivals like Cullinet, its competition now comes from aggressive upstarts like Sybase and Gupta as well as a rejuvenated Informix.
As far as the media is concerned, the main reason Linux is a credible challenge is because it is getting vocal and financial support from major corporations like Intel, IBM, Oracle, Informix, and Corel.