A brief anecdote:
I prepared a presentation yesterday to present today to colleagues on subjects such as Continuous Integration, Unit / Spec Testing, Source management, etc.
I created the presentation in MS PowerPoint 2010, and saved it with some embedded fonts in .pptx format. It runs great. I open it on my work PC this morning, and it runs great. I save it to a thumb drive, and it opens fine.
We get into the conference room late, I log onto the PC that’s there, I open the presentation.. …and PowerPoint crashes.
I try copying it from the USB Drive to the Desktop, I open it …and PowerPoint crashes again.
Luckily, I saved a version in .ppt format so that it would be backwards compatible with PowerPoint 2000-2003. I open that …and PowerPoint crashes again.
Luckily, I also uploaded the presentation to SlideShare. I attempt to open that …and the computer has trouble connecting to the internet.
Luckily, I had also exported the presentation to a PDF file. I open that in Adobe Acrobat Reader, put it in full-screen mode, and gave the presentation.
I hope that illustrates the point well enough without further explanation.