Most people know that Adobe wants to make Acrobat the universal tool for all file formats on the web.  Thus, a few years ago they started to include technology to handle the myriad of 3D CAD formats, such as Catia, Pro/E, NX, etc.  After fumbling with some half-baked tools from Right Hemisphere, Adobe decided to acquire the premier company that made CAD import libraries: TTF.  The TTF-developed format, known as PRC, was incorporated in the tool known as Acrobat Pro Extended (APEX).

Many organizations pursuing the model-based enterprise (US Army, Boeing) started adopting APEX as a key enabler.  They had grown tired of the unfulfilled promises of STEP, and they were pleased to see a tool that could fully view 3D PMI.  As a result, the PRC format has emerged as sort of a de facto standard for sharing CAD models.

In Q4 2009, Adobe decided that trying to keep up with all of the dynamic 3D formats was too much for a company creating tools for tens of millions of users.  Thus, the word on the street is the they will continue to embed PRC in Acrobat, but they are spinning-out the technlogy to one of their 3D partner companies,  This company will continue to develop the PRC technology and Adobe will license it back and use it in their Acrobat tools.

This sounds like a win-win situation to me.